Podcast
Questions and Answers
What is a critical distinction between macroemulsions and microemulsions regarding their formation?
What is a critical distinction between macroemulsions and microemulsions regarding their formation?
- Microemulsions are thermodynamically unstable, needing constant energy to maintain their structure, unlike macroemulsions.
- Macroemulsions form spontaneously, while microemulsions require substantial energy input.
- Microemulsions form spontaneously with carefully selected surfactants, while macroemulsions require significant energy input. (correct)
- Macroemulsions are always transparent, whereas microemulsions exhibit a white opaque appearance due to their formation process.
What is the underlying principle of the oriented-wedge theory in explaining emulsion formation?
What is the underlying principle of the oriented-wedge theory in explaining emulsion formation?
- Emulsifying agents reduce interfacial tension by forming spherical shapes, minimizing surface area.
- Emulsifying agents create a thick, rigid film at the interface, preventing coalescence of the dispersed phase.
- Emulsifying agents increase the surface tension between two immiscible liquids, stabilizing the emulsion.
- Emulsifying agents position themselves based on their solubility, with hydrophilic portions oriented towards water and hydrophobic portions towards oil. (correct)
What is the crucial role of nonionic emulsifiers, and why are they preferred in certain pharmaceutical formulations?
What is the crucial role of nonionic emulsifiers, and why are they preferred in certain pharmaceutical formulations?
- They exhibit a pH-dependent charge, allowing for controlled emulsion stability in various physiological conditions and are used to enhance drug solubility.
- They create a highly rigid interfacial film, providing exceptional stability against coalescence and are used to control drug release rates.
- They carry a charge that stabilizes emulsions through electrostatic repulsion and are preferred for their strong antimicrobial properties.
- They do not ionize, which avoids interference with other ionic ingredients, and are valued for their stability across a wide range of pH and electrolyte concentrations. (correct)
During the preparation of an emulsion using the dry gum method, what is the most critical factor for achieving a stable primary emulsion?
During the preparation of an emulsion using the dry gum method, what is the most critical factor for achieving a stable primary emulsion?
What is the main reason for the instability of pharmaceutical emulsions, and which strategy is most effective in addressing this issue?
What is the main reason for the instability of pharmaceutical emulsions, and which strategy is most effective in addressing this issue?
What is the most critical consideration regarding the impact of temperature on emulsion stability, and how does it influence long-term storage?
What is the most critical consideration regarding the impact of temperature on emulsion stability, and how does it influence long-term storage?
What role does the Hydrophile-Lipophile Balance (HLB) system play in formulating stable emulsions, and how is it applied in practice?
What role does the Hydrophile-Lipophile Balance (HLB) system play in formulating stable emulsions, and how is it applied in practice?
What is the correct procedure for calculating the required amounts of Tween 80 (HLB 15) and Span 80 (HLB 4.3) to achieve a stable liquid paraffin o/w emulsion with a required HLB of 10.5, given 5g of total emulsifying agents are needed?
What is the correct procedure for calculating the required amounts of Tween 80 (HLB 15) and Span 80 (HLB 4.3) to achieve a stable liquid paraffin o/w emulsion with a required HLB of 10.5, given 5g of total emulsifying agents are needed?
What is the primary consideration for choosing between o/w and w/o emulsions for topical applications, particularly concerning medicinal agents and skin conditions?
What is the primary consideration for choosing between o/w and w/o emulsions for topical applications, particularly concerning medicinal agents and skin conditions?
What is the critical implication of an emulsion cracking or breaking, and why is this phenomenon irreversible?
What is the critical implication of an emulsion cracking or breaking, and why is this phenomenon irreversible?
What is a crucial advantage of administering drugs via rectal suppositories compared to oral administration, especially for drugs susceptible to first-pass metabolism?
What is a crucial advantage of administering drugs via rectal suppositories compared to oral administration, especially for drugs susceptible to first-pass metabolism?
What is the most significant physiological factor affecting drug absorption from rectal suppositories, and how does it influence drug bioavailability?
What is the most significant physiological factor affecting drug absorption from rectal suppositories, and how does it influence drug bioavailability?
How does the lipid-water partition coefficient of a drug influence the choice of a suppository base, and what outcome can be anticipated?
How does the lipid-water partition coefficient of a drug influence the choice of a suppository base, and what outcome can be anticipated?
What advantage do polyethylene glycol (PEG) suppository bases offer over cocoa butter bases, especially concerning drug release and storage?
What advantage do polyethylene glycol (PEG) suppository bases offer over cocoa butter bases, especially concerning drug release and storage?
In the context of suppository formulation, what is the practical significance of the displacement value (DV), and how is it applied during the compounding process?
In the context of suppository formulation, what is the practical significance of the displacement value (DV), and how is it applied during the compounding process?
Why should cocoa butter be slowly and evenly melted, preferably over a bath of warm water, when preparing suppositories?
Why should cocoa butter be slowly and evenly melted, preferably over a bath of warm water, when preparing suppositories?
Calculate the amount of theobroma oil needed to prepare 10 suppositories, each using a 2g mold and containing 400mg of zinc oxide (Displacement value = 4.7).
Calculate the amount of theobroma oil needed to prepare 10 suppositories, each using a 2g mold and containing 400mg of zinc oxide (Displacement value = 4.7).
What strategies are employed to ensure the stability and therapeutic effectiveness of vaginal suppositories, especially those designed to maintain a healthy vaginal environment?
What strategies are employed to ensure the stability and therapeutic effectiveness of vaginal suppositories, especially those designed to maintain a healthy vaginal environment?
What are the consequences of storing suppositories improperly, particularly those made with glycerinated gelatin versus those made with polyethylene glycol (PEG)?
What are the consequences of storing suppositories improperly, particularly those made with glycerinated gelatin versus those made with polyethylene glycol (PEG)?
What is the crucial difference between urethral suppositories for males versus females, and how does this difference accommodate anatomical and physiological variances?
What is the crucial difference between urethral suppositories for males versus females, and how does this difference accommodate anatomical and physiological variances?
What is the role and required procedure for hand rolling and shaping suppositories?
What is the role and required procedure for hand rolling and shaping suppositories?
What challenge is associated with the use of glycerinated gelatin as a suppository base, and how can this challenge be mitigated to ensure patient comfort and efficacy?
What challenge is associated with the use of glycerinated gelatin as a suppository base, and how can this challenge be mitigated to ensure patient comfort and efficacy?
What is a key advantage of using vaginal tablets (inserts) over traditional vaginal suppositories, specifically relating to manufacturing, stability, and patient experience?
What is a key advantage of using vaginal tablets (inserts) over traditional vaginal suppositories, specifically relating to manufacturing, stability, and patient experience?
What’s the best way to prepare oral emulsions?
What’s the best way to prepare oral emulsions?
What role does surface tension play in the theories of emulsification?
What role does surface tension play in the theories of emulsification?
What is a key consideration when using finely divided solids as emulsifying agents?
What is a key consideration when using finely divided solids as emulsifying agents?
How do intravenous emulsions deliver nutritive oil and oil-soluble vitamins, and what type of emulsion is crucial for intravenous administration?
How do intravenous emulsions deliver nutritive oil and oil-soluble vitamins, and what type of emulsion is crucial for intravenous administration?
How does the incorporation of auxiliary emulsifying agents (like high molecular weight alcohols such as stearyl alcohol/cetyl alcohol) enhance the stability of emulsions?
How does the incorporation of auxiliary emulsifying agents (like high molecular weight alcohols such as stearyl alcohol/cetyl alcohol) enhance the stability of emulsions?
What is the role of light-resistant containers when storing therapeutic emulsions?
What is the role of light-resistant containers when storing therapeutic emulsions?
Using what theories of emulsification will surface-active agents help the breaking up of large globules into smaller ones?
Using what theories of emulsification will surface-active agents help the breaking up of large globules into smaller ones?
What steps below can be taken to enhance the stability of an emulsion?
What steps below can be taken to enhance the stability of an emulsion?
What should the vehicle for a liniment comprise, and what caution must accompany its use and labeling?
What should the vehicle for a liniment comprise, and what caution must accompany its use and labeling?
You are asked to compound 8 codeine phosphate suppositories (D.V=1.1) using a 1g mold size. The final suppository should have 60mg of codeine phosphate. Prepare 10 suppositories to compensate for any loss. How much base should you use?
You are asked to compound 8 codeine phosphate suppositories (D.V=1.1) using a 1g mold size. The final suppository should have 60mg of codeine phosphate. Prepare 10 suppositories to compensate for any loss. How much base should you use?
Calculate the amount of Glycerin gelatin Base required to prepare six AMINOPHYLLINE (Displacement value = 1.3) suppositories. Tthe final result needs to use a 4 g mold, and the final product should contain 100 mg of aminophylline in each suppository.
Calculate the amount of Glycerin gelatin Base required to prepare six AMINOPHYLLINE (Displacement value = 1.3) suppositories. Tthe final result needs to use a 4 g mold, and the final product should contain 100 mg of aminophylline in each suppository.
Following insertion, what scenario would MOST likely impair the release of a drug from a suppository base?
Following insertion, what scenario would MOST likely impair the release of a drug from a suppository base?
What is the MOST significant physicochemical property of a drug influencing its release from a suppository base?
What is the MOST significant physicochemical property of a drug influencing its release from a suppository base?
In the context of selecting an appropriate route for drug administration, what is the MOST critical advantage of utilizing rectal suppositories for systemic drug delivery?
In the context of selecting an appropriate route for drug administration, what is the MOST critical advantage of utilizing rectal suppositories for systemic drug delivery?
Which of the following BEST describes the rationale for buffering vaginal suppositories to an acidic pH of approximately 4.5?
Which of the following BEST describes the rationale for buffering vaginal suppositories to an acidic pH of approximately 4.5?
What is the MOST crucial consideration for the long-term storage of glycerinated gelatin suppositories?
What is the MOST crucial consideration for the long-term storage of glycerinated gelatin suppositories?
For which scenario is the displacement value (DV) MOST critical in suppository formulation?
For which scenario is the displacement value (DV) MOST critical in suppository formulation?
How does the hand-rolling method compare to other suppository preparation methods?
How does the hand-rolling method compare to other suppository preparation methods?
What is the MOST significant challenge posed by cocoa butter's polymorphic behavior in suppository formulation, and how can it be effectively addressed?
What is the MOST significant challenge posed by cocoa butter's polymorphic behavior in suppository formulation, and how can it be effectively addressed?
What is the MAIN reason that polyethylene glycol (PEG) suppository bases do not typically require refrigeration?
What is the MAIN reason that polyethylene glycol (PEG) suppository bases do not typically require refrigeration?
What is the MOST critical consideration when determining a suitable liniment vehicle that contains insoluble matter?
What is the MOST critical consideration when determining a suitable liniment vehicle that contains insoluble matter?
In the production of emulsions, what is the fundamental role of surface-active agents (surfactants) according to the surface tension theory?
In the production of emulsions, what is the fundamental role of surface-active agents (surfactants) according to the surface tension theory?
Which of the following properties is MOST crucial for ensuring the stability and efficacy of an emulsion intended for topical application?
Which of the following properties is MOST crucial for ensuring the stability and efficacy of an emulsion intended for topical application?
In the calculation of the required Hydrophile-Lipophile Balance (HLB) for a blend of two surfactants, what assumption is made?
In the calculation of the required Hydrophile-Lipophile Balance (HLB) for a blend of two surfactants, what assumption is made?
Why is a mortar with a rough inner surface preferred over a smooth glass mortar when preparing emulsions using the dry gum method?
Why is a mortar with a rough inner surface preferred over a smooth glass mortar when preparing emulsions using the dry gum method?
What is the MOST critical consideration regarding the temperature of the aqueous and oil phases when preparing emulsions, especially when the formulation contains solid or semisolid components?
What is the MOST critical consideration regarding the temperature of the aqueous and oil phases when preparing emulsions, especially when the formulation contains solid or semisolid components?
In the context of emulsion instability, what is the underlying mechanism of 'coalescence', and how does it ultimately lead to 'breaking' of the emulsion?
In the context of emulsion instability, what is the underlying mechanism of 'coalescence', and how does it ultimately lead to 'breaking' of the emulsion?
What is the primary reason for using light-resistant containers and including antioxidants in therapeutic emulsions?
What is the primary reason for using light-resistant containers and including antioxidants in therapeutic emulsions?
How does the 'oriented-wedge theory' explain the formation of emulsions, and on what assumption does it rely?
How does the 'oriented-wedge theory' explain the formation of emulsions, and on what assumption does it rely?
What is the role of high molecular weight alcohols (like stearyl or cetyl alcohol) as auxiliary emulsifying agents in emulsions?
What is the role of high molecular weight alcohols (like stearyl or cetyl alcohol) as auxiliary emulsifying agents in emulsions?
Why must alcohol or alcohol-containing solutions not be directly added to a primary emulsion prepared with gums like acacia?
Why must alcohol or alcohol-containing solutions not be directly added to a primary emulsion prepared with gums like acacia?
What distinguishes microemulsions from macroemulsions, particularly influencing their behavior in pharmaceutical applications?
What distinguishes microemulsions from macroemulsions, particularly influencing their behavior in pharmaceutical applications?
What is the underlying principle of the 'plastic or interfacial film theory' in stabilizing emulsions?
What is the underlying principle of the 'plastic or interfacial film theory' in stabilizing emulsions?
Under what circumstance is the Bottle or Forbes bottle method MOST appropriate for preparing emulsions?
Under what circumstance is the Bottle or Forbes bottle method MOST appropriate for preparing emulsions?
How do rectal fluids' characteristics, particularly their pH and buffering capacity, affect drug absorption from suppositories?
How do rectal fluids' characteristics, particularly their pH and buffering capacity, affect drug absorption from suppositories?
What is the advantage of using polyethylene glycol (PEG) as a suppository base material compared to cocoa butter, especially in terms of drug release?
What is the advantage of using polyethylene glycol (PEG) as a suppository base material compared to cocoa butter, especially in terms of drug release?
What is the primary advantage of using vaginal tablets (inserts) over traditional vaginal suppositories regarding patient convenience and product stability?
What is the primary advantage of using vaginal tablets (inserts) over traditional vaginal suppositories regarding patient convenience and product stability?
Which approach BEST addresses the need for a stable emulsion with both short-term and long-term stability?
Which approach BEST addresses the need for a stable emulsion with both short-term and long-term stability?
What physiological factor significantly impacts drug absorption from rectal suppositories due to its limited presence?
What physiological factor significantly impacts drug absorption from rectal suppositories due to its limited presence?
What is the MOST important factor to consider when choosing between an o/w and w/o emulsion for a topical dermatological product?
What is the MOST important factor to consider when choosing between an o/w and w/o emulsion for a topical dermatological product?
How can the stability of an emulsion suffering from creaming be BEST improved without changing the formulation drastically?
How can the stability of an emulsion suffering from creaming be BEST improved without changing the formulation drastically?
You are asked to prepare tetracaine HCl suppositories (D.V=1.2) using 2g cocoa butter as the base. The final suppository formulation should contain 40mg of powder. If you are preparing 12, how much base will you need?
You are asked to prepare tetracaine HCl suppositories (D.V=1.2) using 2g cocoa butter as the base. The final suppository formulation should contain 40mg of powder. If you are preparing 12, how much base will you need?
You prepare 8 suppositories from a Glycerin gelatin Base and now need to package it. What is the BEST way to package it to ensure quality?
You prepare 8 suppositories from a Glycerin gelatin Base and now need to package it. What is the BEST way to package it to ensure quality?
Which of the following is the MOST essential consideration in selecting a suppository base to ensure optimal drug bioavailability?
Which of the following is the MOST essential consideration in selecting a suppository base to ensure optimal drug bioavailability?
An industrial pharmacist is scaling up the production of a topical emulsion. What is the most crucial factor during large scale preparation?
An industrial pharmacist is scaling up the production of a topical emulsion. What is the most crucial factor during large scale preparation?
In the preparation of ophthalmic emulsions, what is MOST crucial for preventing irritation?
In the preparation of ophthalmic emulsions, what is MOST crucial for preventing irritation?
What is a critical consideration in the formulation of water-in-oil (w/o) emulsions for intramuscular injection to achieve a prolonged drug effect?
What is a critical consideration in the formulation of water-in-oil (w/o) emulsions for intramuscular injection to achieve a prolonged drug effect?
Why are nonionic surfactants, known for their stability across a wide range of pH and ionic strengths, not universally preferred in all emulsion formulations?
Why are nonionic surfactants, known for their stability across a wide range of pH and ionic strengths, not universally preferred in all emulsion formulations?
What is the key reason for the instability observed when alcohol or alcohol-containing solutions are directly added to a primary emulsion stabilized with gums like acacia?
What is the key reason for the instability observed when alcohol or alcohol-containing solutions are directly added to a primary emulsion stabilized with gums like acacia?
What is the most significant implication of phase inversion in an emulsion, and how does it affect the product's performance and stability?
What is the most significant implication of phase inversion in an emulsion, and how does it affect the product's performance and stability?
In the context of dermatological formulations, what is the critical advantage of utilizing emulsions with diminished particle size (nanoemulsions) regarding percutaneous absorption?
In the context of dermatological formulations, what is the critical advantage of utilizing emulsions with diminished particle size (nanoemulsions) regarding percutaneous absorption?
What is the most crucial consideration for the long-term storage of emulsions intended for intravenous administration, particularly regarding the prevention of coalescence?
What is the most crucial consideration for the long-term storage of emulsions intended for intravenous administration, particularly regarding the prevention of coalescence?
What is the primary reason for employing multiple emulsions (such as w/o/w) in drug delivery systems, especially for controlled release applications?
What is the primary reason for employing multiple emulsions (such as w/o/w) in drug delivery systems, especially for controlled release applications?
What is the crucial underlying principle of the conductivity test that enables differentiation between o/w and w/o emulsions?
What is the crucial underlying principle of the conductivity test that enables differentiation between o/w and w/o emulsions?
Calculate the precise amount of cocoa butter required to prepare 10 suppositories, each utilizing a 2 g mold and containing 500 mg of a drug with a displacement value of 1.5.
Calculate the precise amount of cocoa butter required to prepare 10 suppositories, each utilizing a 2 g mold and containing 500 mg of a drug with a displacement value of 1.5.
What is the key rationale behind the addition of vanillin and alcohol in the formulation of Mineral Oil Emulsion, beyond their flavoring properties?
What is the key rationale behind the addition of vanillin and alcohol in the formulation of Mineral Oil Emulsion, beyond their flavoring properties?
What is the underlying reason for buffering Vaginal suppositories to an acidic pH of approximately 4.5, consistent with the normal vaginal environment?
What is the underlying reason for buffering Vaginal suppositories to an acidic pH of approximately 4.5, consistent with the normal vaginal environment?
What is the key rationale for using polyethylene glycol (PEG) as a suppository base material, particularly concerning drug release characteristics?
What is the key rationale for using polyethylene glycol (PEG) as a suppository base material, particularly concerning drug release characteristics?
A pharmacist must prepare 10 aminophylline suppositories, each using a 4g mold and containing 150mg of aminophylline, with a displacement value of 1.3. Given a glycerinated gelatin base is used, that itself has a density 1.2 times greater than theobroma oil, calculate the amount of glycerinated gelatin base required.
A pharmacist must prepare 10 aminophylline suppositories, each using a 4g mold and containing 150mg of aminophylline, with a displacement value of 1.3. Given a glycerinated gelatin base is used, that itself has a density 1.2 times greater than theobroma oil, calculate the amount of glycerinated gelatin base required.
What is the BEST method to handle cocoa butter when preparing suppositories in order to prevent the formation of unstable crystalline forms?
What is the BEST method to handle cocoa butter when preparing suppositories in order to prevent the formation of unstable crystalline forms?
What is the primary reason commercial suppositories are individually wrapped in foil or plastic?
What is the primary reason commercial suppositories are individually wrapped in foil or plastic?
What is a crucial advantage of administering drugs via rectal suppositories, particularly for highly unstable APIs?
What is a crucial advantage of administering drugs via rectal suppositories, particularly for highly unstable APIs?
What is the rationale for using the dry gum method over the wet gum method when preparing emulsions containing a mixture of fixed and volatile oils?
What is the rationale for using the dry gum method over the wet gum method when preparing emulsions containing a mixture of fixed and volatile oils?
What is the significance of lymphatic circulation in the context of drug absorption from rectal suppositories for achieving systemic effects?
What is the significance of lymphatic circulation in the context of drug absorption from rectal suppositories for achieving systemic effects?
What is the underlying assumption when calculating the HLB for a mixture of surfactants in emulsion formulation?
What is the underlying assumption when calculating the HLB for a mixture of surfactants in emulsion formulation?
Flashcards
Emulsion
Emulsion
A thermodynamically unstable disperse system of two immiscible liquids, one dispersed as minute globules in the other.
Oil-in-Water (o/w) Emulsion
Oil-in-Water (o/w) Emulsion
An emulsion where an oleaginous or oily component is dispersed within an aqueous external phase.
Water-in-Oil (w/o) Emulsion
Water-in-Oil (w/o) Emulsion
An emulsion consists of water or an aqueous component, dispersed within an oleaginous external phase.
Multiple Emulsions
Multiple Emulsions
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Microemulsions
Microemulsions
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Macroemulsions
Macroemulsions
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Miscibility Test
Miscibility Test
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Staining test
Staining test
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Conductivity test
Conductivity test
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Purpose of Emulsions
Purpose of Emulsions
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Disadvantages of Emulsions
Disadvantages of Emulsions
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Surface Tension Theory
Surface Tension Theory
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Oriented-Wedge Theory
Oriented-Wedge Theory
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Interfacial Film Theory
Interfacial Film Theory
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Criteria for selecting emulsifiers
Criteria for selecting emulsifiers
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Carbohydrate Materials
Carbohydrate Materials
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Protein Substances
Protein Substances
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High Molecular Weight Alcohols
High Molecular Weight Alcohols
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Surfactants
Surfactants
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Finely Divided Solids
Finely Divided Solids
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Hydrophilic-Lipophilic Balance (HLB)
Hydrophilic-Lipophilic Balance (HLB)
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HLB Values (3 to 6)
HLB Values (3 to 6)
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HLB Values (8 to 18)
HLB Values (8 to 18)
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Required HLB
Required HLB
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Continental or Dry Gum Method
Continental or Dry Gum Method
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English or Wet Gum Method
English or Wet Gum Method
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Bottle or Forbes Bottle Method
Bottle or Forbes Bottle Method
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In Situ Soap Method
In Situ Soap Method
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Flocculation
Flocculation
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Creaming
Creaming
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Coalescence and Breaking
Coalescence and Breaking
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Phase Inversion
Phase Inversion
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Suppositories
Suppositories
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Suppository Uses
Suppository Uses
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Glycerin Suppositories
Glycerin Suppositories
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Advantages of Rectal Route for Systemic Effects
Advantages of Rectal Route for Systemic Effects
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Physiological factors that affect rectal absorption of a drug
Physiological factors that affect rectal absorption of a drug
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Colonic Content Effect
Colonic Content Effect
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Circulation Route
Circulation Route
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Physicochemical Factors of the Drug
Physicochemical Factors of the Drug
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Physicochemical Factors of the Base
Physicochemical Factors of the Base
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Fatty bases
Fatty bases
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Glycerinated gelatin
Glycerinated gelatin
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Water-Soluble Bases
Water-Soluble Bases
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Suppository Preparation Methods
Suppository Preparation Methods
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Preparation by Molding
Preparation by Molding
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Preparation by Compression
Preparation by Compression
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Displacement Value (DV)
Displacement Value (DV)
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Vaginal Inserts advantages
Vaginal Inserts advantages
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Study Notes
Pharmaceutical Emulsions
- Thermodynamically unstable systems with two immiscible liquids
- One liquid dispersed as minute globules (droplets) throughout the other
- The dispersed phase is the internal phase
- The dispersion medium is the external or continuous phase
- Stable emulsions require an emulsifying agent
Emulsion Types
- Oil-in-Water (o/w): Oily internal phase dispersed in an aqueous external phase
- Water-in-Oil (w/o): Aqueous internal phase dispersed in an oleaginous external phase
- O/w emulsions can be diluted with water
- W/o emulsions can be diluted with oil
- Multiple emulsions: Multiple layers of dispersed and continuous phases like oil-in-water-in-oil (o/w/o) and water-in-oil-in-water (w/o/w)
Macroemulsions vs. Microemulsions
- Macroemulsions droplet size ~5,000 Ã…, white opaque appearance, thermodynamically unstable, requires substantial energy for production
- Microemulsions droplet size 100-1,000 Ã…, cloudy/translucent/transparent, thermodynamically stable, forms spontaneously
- Microemulsions enhance oral drug delivery and transdermal drug delivery with rapid absorption due to small droplet size
Determination Tests of Emulsion Type
- Miscibility test: o/w emulsions are stable upon dilution with water, w/o emulsions with oil
- Staining test: Oil-soluble stain identifies the external phase under a microscope
- Staining globules and colorless medium = o/w emulsion
- Staining background and colorless globules = w/o emulsion
- Conductivity test: Water as a continuous phase conducts electricity
Classification of Emulsions According to Physical State and Route of Administration
- Liquid emulsions can be administered orally (o/w), topically (lotion), or parenterally (I.V. o/w, I.M. and S.C. w/o)
- Semisolid emulsions are used topically (lotions, creams, liniments)
Purpose and Benefits of Emulsions
- Improve drug administration by mixing immiscible liquids
- Orally administered o/w emulsions improve palatability via taste masking and act as carriers for lipophilic drugs, enhancing oral bioavailability
- Sterile I.V. o/w emulsions deliver nutritive oil and oil-soluble vitamins
- Intramuscular/subcutaneous w/o emulsions prolong drug effects
- Topical emulsions (o/w or w/o) facilitate percutaneous absorption
- O/w emulsions are easily removed from the skin with water and are suitable for easily irritating medications
- W/o emulsions soften skin and resist drying/removal by water
Acceptable Emulsion Characteristics
- Uniform distribution of dispersed phase globules
- Pleasing appearance and texture
- Appropriate flavor for oral administration
- Easy spreadability for external application
- Physical stability (no flocculation, creaming, sedimentation, coalescence)
- Absence of microbial deterioration
Disadvantages of Emulsions
- Thermodynamically unstable, requires careful formulation
- Requires thorough shaking before dosing
- Storage conditions affect stability
- Risk of microbial contamination
- Bulky compared to solid dosage forms
Gibbs Free Energy in an Emulsion
- ΔG = ΔA γ, where A is the surface area of dispersed particles and γ is interfacial tension
- Stable emulsions have large A and small G; decreasing γ decreases G and self-attraction of dispersed phase particles
Theories of Emulsification
- Surface Tension Theory: Emulsifying agents lower the interfacial tension between immiscible liquids
- Facilitate the breakup of large globules into smaller ones, reducing their tendency to reunite
- Oriented-Wedge Theory: Emulsifying agents form monomolecular layers around droplets
- Hydrophilic emulsifiers promote o/w emulsions, while hydrophobic emulsifiers favor w/o emulsions
- The phase in which the emulsifier is more soluble becomes the continuous phase
- Plastic or Interfacial Film Theory: Emulsifying agents create a thin film at the interface, preventing contact and coalescence
Factors Affecting Emulsion Formation
- Emulsifying agents
- pH
- Ratio of internal to external phases.
Criteria for Selecting Emulsifying Agents
- Compatibility: No interference with therapeutic agents or stability
- Stability: No deterioration during preparation or storage
- Safety: Nontoxic, minimal odor/taste/color
- Promotion of Emulsification: Ensure effective dispersion
Common Types of Emulsifying Agents
- Carbohydrate Materials: Acacia, tragacanth, agar (o/w emulsions)
- Protein Substances: Gelatin, egg white, casein (o/w emulsions)
- High Molecular Weight Alcohols: Stearyl alcohol, cetyl alcohol (o/w stabilizers)
- Surfactants: Amphiphilic molecules with hydrophilic heads and lipophilic tails (o/w or w/o emulsions)
- Anionic (e.g., organic soaps, sulfonates)
- Cationic (e.g., cetrimide, benzalkonium chloride)
- Nonionic (e.g., Span, Tween)
- Finely Divided Solids: Bentonite, magnesium hydroxide (o/w or w/o emulsions)
- Volume of each phase is critical
Mechanisms of Action of Emulsifying Agents
- Monomolecular: Lower interfacial tension and stabilize emulsion (e.g., Potassium laurate, Tween)
- Multimolecular: Strong rigid film preventing coalescence (e.g., Acacia, Gelatin)
- Solid Particles: Film formed by ionized solid particles (e.g., Bentonite, Magnesium hydroxide)
- Auxiliary: Lipophilic (High molecular weight alcohols) and Hydrophilic(Tragacanth and agar )
Hydrophilic-Lipophilic Balance (HLB) System
- Classifies emulsifying agents based on their chemical makeup
- Each agent is assigned an HLB value (1-20, usual rage) indicating polarity
- HLB 3-6: Lipophilic, favor w/o emulsions
- HLB 8-18: Hydrophilic, favor o/w emulsions
- HLB for various activities:
- Antifoaming: 1-3
- Emulsifiers (w/o): 3-6
- Wetting agents: 7-9
- Emulsifiers (o/w): 8-18
- Solubilizers: 15-20
- Detergents: 13-16
Required HLB
- Emulsifying agents should have the same or nearly the same HLB value as the oleaginous phase
- All oils, waxes and other materials likely to be incorporated into emulsions have an individual "Required HLB."
- Mineral oil has an assigned HLB value of 4 for w/o emulsion and 10.5 for o/w emulsion
Blending Emulsifying Agents and Calculations in the HLB System
- HLB values are additive for surfactant mixtures
- Total HLB = HLB A (fraction A) + HLB B (fraction B) Example:
- Liquid paraffin (required HLB 10.5) 50g
- Emulsifying agents 5g
- Water to 100g
- Fraction of Tween 80 (HLB of 15) and Span 80 (HLB of 4.3) used to produce a physically stable liquid paraffin emulsion:Tween 80 = 2.9 g, Span 80 = 2.1 g
Preparation Methods
Small-Scale Emulsion Preparation Methods
- Laboratory Equipment: mortar and pestle, blenders, hand homogenizers, prescription bottles
- Laboratory Techniques:
- Continental or dry gum method (4:2:1): Triturate emulsifying agent with oil, then add water
- English or wet gum method: Create mucilage with water, then slowly incorporate oil
- Bottle or Forbes bottle method: Shake mixture in a capped bottle (for volatile oils or low viscosity Substances)
Important Considerations on Emulsion Preparation
- Dissolve water-soluble ingredients in the aqueous phase
- Dissolve oil-soluble components in the oil phase
- Add solid substances as solutions to the primary emulsion
- Raise aqueous phase temperature 2-3°C above oil phase temperature to prevent crystallization
- Add any substance that interferes with stability of emulsion at the end
- Forbes bottle method is not suitable for viscous oils because they cannot be thoroughly agitated in the bottle when mixed with the emulsifying agent.
- When the intended dispersed phase is a mixture of fixed oil and volatile oil, the dry gum method should be employed
Auxiliary Methods
- Hand homogenizer to reduce globule size to about 5 μm
- In Situ Soap Method (Nascent soap method):
- Calcium soaps (w/o emulsions): Vegetable oils (oleic acid) + limewater
- Soft soaps
Large-Scale Preparation
- Mixing tanks with high-speed impellers
- Colloid mills or large homogenizers refine the emulsion further
Stability of Emulsions
- Instability: Flocculation, creaming/sedimentation, coalescence/aggregation, cracking/breaking, phase separation (inversion)
- Flocculation: Droplets aggregate to form clumps
- Creaming: Aggregates rise/settle, reversible with agitation (Stokes equation: factors affecting separation rate)
- Coalescence: Droplets merge into larger droplets, leading to phase separation (breaking), irreversible
- Phase Inversion: o/w to w/o emulsion (occurs when the dispersed phase exceed a theoretical maximum of 74% of the total volume)
Consideration for temperature, light, environmental factors and storage
- Store at controlled room temperature, and not under direct sunlight
- Preserve with fungistatic preservatives (methylparaben, propylparaben) or Alcohol (12% to 15%)
Therapeutic Examples of Oral and Topical Emulsions
Oral Emulsions
- Mineral Oil Emulsion: Lubricating cathartic
- Castor Oil Emulsion: Laxative
- Simethicone Emulsion: Defoaming agent for gas relief
Topical Emulsions
- Lotions: Hand and body lotions (o/w)
- Shampoos: Solution, emulsion, or suspension for hair and scalp
- Liniments: Alcoholic/oleaginous solutions/emulsions, external use only
Suppositories
- Solid dosage forms for insertion into body orifices
- Melt, soften, or dissolve, exerting local or systemic effects
- Used rectally, vaginally, occasionally urethrally
Suppository Shapes
- Rectal: Cylindrical, tapered (32 mm long, ~2 g with cocoa butter)
- Vaginal: Globular, oviform, cone-shaped (~5 g with cocoa butter)
- Urethral: Slender, pencil-shaped (male: 140 mm, female: 70 mm)
Fate of the Suppository
- Base melts, softens, or dissolves, distributing medicaments
- Immediate or sustained release
- May be prepared for long-acting purposes
Local Rectal Suppositories
- Relieve constipation (glycerin suppositories)
- Treat pain, irritation, itching, inflammation (anti-hemorrhoidal suppositories)
Local Vaginal Suppositories
- Contraceptives (nonoxynol-9)
- Antiseptics (feminine hygiene)
- Antifungals (Candida albicans), anti-infectives/antibiotics
Systemic Effect of Rectal Suppositories
- Advantages over oral: bypasses stomach/intestine/liver, avoids irritation, convenient for patients unable to swallow, effective for patients with vomiting
- Examples: Prochlorperazine, indomethacin, ondansetron
- Dose depends on drug properties, physiological barriers, and the ability of formulation to release the drug
Rectal Absorption
- Affected by physiological and physicochemical factors
Physiological Factors
- Human rectum is 15-20 cm long, contains 2-3 mL of mucous fluid
- No villi or microvilli, abundant vascularization
Colonic Content
- Greater absorption from an empty rectum
- Evacuation enema may be used to remove fecal matter
Circulation Route
- Bypasses portal circulation, avoiding liver metabolism
- Lower hemorrhoidal veins and lymphatic circulation
pH and Lack of Buffering Capacity of the Rectal Fluids
- Neutral pH (pH 7) with no effective buffer capacity
- Suppository base significantly influences drug release
Physicochemical Factors of the Drug and Suppository Base
- Drug: Lipid/water solubility, particle size, amount of drug, pKa of the drug
- Base: Melting/softening/dissolving ability, drug release ability, hydrophilic/hydrophobic properties, rheological properties
Lipid-Water Solubility of Drug
- Lipophilic drugs in fatty bases have less tendency to escape
- Water-soluble bases release both water- and oil-soluble drugs
Drug solubility and suppository formulation
- Fat & Low, Water & High = Fatty base
- Fat & High, Water & Low = Aqueous base
- Fat & Low, Water & Low = Intermediate
Amount of Drug
- More drug increases absorption, but absorption rate plateaus above a certain concentration
Particle Size
- Smaller particle size increases dissolution rate and absorption
Nature of the Base
- Must melt, soften, or dissolve to release drug
- Should not interact with the drug or irritate mucous membranes
Properties of the Ideal Suppository Base
- Nontoxic, non-irritating
- Inert and compatible with medicaments
- Stable during storage
- Easily manufactured
- Dissolves/disintegrates quickly at body temperature
- Solidifies rapidly
- Contracts on cooling
- Has wetting and emulsifying properties
Main Types of Suppository Bases
- Fatty (oleaginous bases): Cocoa butter, hydrogenated vegetable oils
- Water-soluble/miscible: Glycerinated gelatin, polyethylene glycol
- Miscellaneous: Combinations of lipophilic and hydrophilic substances
Fatty or Oleaginous Bases
- Cocoa butter (Theobroma oil): Melts quickly at body temperature, immiscible with body fluids
- Hydrogenated fatty acids of vegetable oils
- Fat-based compounds (esters of glycerin with palmitic and stearic acids)
Cocoa Butter, NF
- Obtained from roasted Theobroma cacao seeds
- Melts at 30°C to 36°C
- Exhibits marked polymorphism (existence in several crystalline forms) because of triglyceride content
Cocoa Butter polymorphism
- Carelessly melted at high temperatures and quickly chilled forms the α-crystals (melts at 22°C)
- Carefully melting at low temperatures forms the β-crystals (stable), that have a greater stability and a higher melting point
- Avoid formation of the unstable crystalline form and ensure retention in the liquid of the more stable beta crystals that will constitute nuclei upon which the congealing may occur during chilling of the liquid
Disadvantages of Theobroma oil:
- Polymorphism, Adherence to mold, Low m.p, Low water absorbance, Stability problem, Not suitable for warm countries, Relatively high cost
Other fatty bases
Include commercial products such as: Fattibase, Wecobee bases, Witepsol bases
Water-Soluble and Water-Miscible Bases
- Glycerinated gelatin & Polyethylene glycols
Glycerinated gelatin suppositories
- Prepare by dissolving gelatin (20%) in glycerin (70%) and water and add the medication solution (10%)
- Most frequently used in preparation of vaginal suppositories, with which prolonged local action of the medicinal agent is usually desired.
- Have a tendency to absorb moisture to hydrate
Glycerinated gelatin suppositories disadvantages
- They must be protected from atmospheric moisture to maintain their shape and consistency.
- may have a dehydrating effect and irritate the tissues upon insertion.
Polyethylene glycols (PEG)
- Polymers of ethylene oxide and water
- PEG suppositories do not melt at body temperature but dissolves slowly in the body
- PEG-based suppositories do not leak from the orifice, as many cocoa butter-based suppositories.
Miscellaneous Bases
- Mixtures of oleaginous and water-soluble/miscible materials
- Include: Polyoxyl 40 stearate, surface-active agents, mixtures of fatty bases with emulsifying agents
Preparation of Suppositories
- Molding from a melt, compression, hand rolling and shaping
Preparation by Molding Steps
- Melting the base
- Incorporating medicaments
- Pouring into molds
- Cooling and congealing
- Removing suppositories from mold
Suppository Molds
- Generally made from stainless steel, aluminum, brass, or plastic Preparation by Compression
- Forcing the mixed mass of the base and the medicaments into special molds using suppository-making machines
- base is combined by thorough mixing, the friction of the process softening the base into a paste-like consistency.
Preparation by Hand Rolling and Shaping
- Oldest and simplest with little need for today's pharmacist to perform
Determination of the Amount of Base Required
- Calculate materials for more suppositories than prescribed to compensate for loss
- If the added amounts of medicaments are slight (less than 100 mg per 2 g suppository weight) , they may be considered to be negligible
Displacement value (D.V)
- Defined as the quantity of drug that displaces one part of the base
- If the density of the drug equals the density of the base, The drug will displace the same amount of base
- If the density of the drug is more than the density of the base, the drug will displace a low amount of base
- If the density of the drug is less than the density of the base the drug will displaces high amount of base
- DV. for liquids equal 1 Example: Calculate the quantities required to make 8 Theobroma oil supp. (2g mold) each containing 400 mg of zinc oxide (DV= 4.7).
-
Calculate the total weight of zinc oxide required. 0.4 X10 = 4g
-
Calculate what weight of base would be required to prepare 10 unmedicated supp.
2g X10 = 20 g
-
Determine what weight of base would be displaced by the medicament. Replaced base = wt. of drug/D.V = 4 / 4.7= 0.85
-
Calculate, therefore, the weight of base required to prepare the medicated supps.
20 – 0.85 = 19.15 g wt. of base required
Calculation for density
- Glycero-gelatin base has a density 1.2 times greater than theobroma oil and glycero-gelatin supp are 1.2g size (1 g supp. mold will produce a 1 g theobroma oil supp.)
Vaginal Suppositories
- Base consists of combinations of PEGs, surfactants, preservative agents
- Buffered to an acid pH of about 4.5
Vaginal inserts
- are prepared by tablet compression and are commonly formulated to contain lactose as the base or filler, a disintegrating agent, a dispersing agent, and a tablet lubricant.
- Some vaginal inserts are capsules of gelatin containing medication
Packaging and Storage
- Individually wrapped in foil or plastic
- Light-sensitive drugs in opaque material
- Store in a cool place
- Cocoa butter suppositories: store below 30°C and preferably in a refrigerator (2°C to 8°C)
- Glycerinated gelatin suppositories: store at a controlled room temperature (20°C to 25°C).
- PEG Suppositories: store at usual room Temperatures
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