Polymorphism in Pharmaceuticals

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Questions and Answers

What is the primary characteristic of polymorphism in substances?

The ability to exist in more than one crystal form

The capacity to dissolve in multiple solvents (correct)

The ability to conduct electricity in solid form

The ability to change color under different conditions

Which method is NOT listed as a way to achieve supersaturation in a solution?

Adding more solute than can dissolve (correct)

Changing the pH of the solution

Lowering the temperature of the solution

Evaporating the solvent

What is the first step in the process of crystallization?

The growth of nuclei into crystals

Creation of crystalline nuclei (correct)

Chemical reaction of components

Cooling the solution rapidly

Which factor does NOT affect the polymorphism of a substance?

Type of crystal formation Signup and view all the answers

What happens to crystal growth when there are many spontaneous nuclei due to rapid cooling?

More, smaller crystals form Signup and view all the answers

What characteristic distinguishes the stable polymorph from the metastable form?

Stable polymorph represents the lowest energy state. Signup and view all the answers

Which method can prevent the spontaneous change of an amorphous drug into a stable crystalline form?

Using a co-solvent like alcohol. Signup and view all the answers

What is a recommended practice when formulating creams and ointments to avoid skin irritation?

Use fine and homogenous substances. Signup and view all the answers

What should be avoided to prevent cake formation in suspensions?

Temperature fluctuations. Signup and view all the answers

If cocoa butter is heated above its melting point, what is the potential outcome?

It will freeze at a higher temperature. Signup and view all the answers

What is the first step in the fusion molding process for suppositories?

Melting the suppository base Signup and view all the answers

What material is used for disposable molds in packing suppositories?

Plastics or aluminum foil Signup and view all the answers

Which condition is NOT recommended for storing suppositories?

At temperatures below 10 °C Signup and view all the answers

What test is used to evaluate the physical strength of suppositories?

Test of softening time Signup and view all the answers

What stability problem is characterized by the deposition of white powder on cocoa butter suppositories?

Blooming Signup and view all the answers

In solids, which characteristic is true regarding intermolecular forces?

They are strong and relatively fixed Signup and view all the answers

Which type of solid is characterized by a well-ordered structure?

Crystalline solid Signup and view all the answers

Which property does NOT apply to solids?

Ability to flow Signup and view all the answers

What effect does rapid cooling have on the size and number of crystals?

Produces many small crystals Signup and view all the answers

Which type of impurities typically decreases crystallization?

Soluble impurities Signup and view all the answers

How does the presence of alcohol in water affect crystallization?

Increases crystallization Signup and view all the answers

What is generally true regarding the stable form of a polymorph?

Has lower potential for conversion Signup and view all the answers

What is the effect of higher viscosity on crystal growth?

It promotes larger crystals with higher growth of nuclei Signup and view all the answers

Which solvent typically results in hydrate crystals?

Water Signup and view all the answers

What are the characteristics of the metastable form of a polymorph?

Has high solubility and lower stability Signup and view all the answers

What happens to a less stable polymorph during the sanding process?

It dissolves while the stable form crystallizes out Signup and view all the answers

What defines a paste in terms of its composition?

Incorporates a high percentage of insoluble particulate solids. Signup and view all the answers

Which of the following is a function of pastes?

To absorb irritating chemicals before they reach the skin. Signup and view all the answers

What is the primary application method for liniments?

Rubbed onto the affected area. Signup and view all the answers

Which of the following is NOT a characteristic of pastes?

They are greasy like ointments. Signup and view all the answers

What kind of ingredients are commonly found in pastes?

Insoluble ingredients like starch and zinc oxide. Signup and view all the answers

Which statement about alcoholic liniments is true?

They are harsher than oily liniments. Signup and view all the answers

Which application area is NOT recommended for pastes?

Hairy parts of the body. Signup and view all the answers

What is the main purpose of using liniments?

To provide a protective coating on the skin. Signup and view all the answers

What characteristic defines absorption ointment bases?

They are hydrophilic and can absorb large amounts of water. Signup and view all the answers

Which of the following is an advantage of absorption bases?

They can incorporate most medications effectively. Signup and view all the answers

What is a primary disadvantage of absorption ointment bases?

They are difficult to remove from the skin. Signup and view all the answers

What is the role of cholesterol in ointment bases?

To enhance the absorption of water in oils and fats. Signup and view all the answers

What distinguishes hydrous lanolin from anhydrous lanolin?

Hydrous lanolin contains additional purified water. Signup and view all the answers

Which component is commonly used as a stiffening agent in pastes and ointments?

Beeswax Signup and view all the answers

Which type of emulsion are water removable bases primarily classified as?

Oil in water type Signup and view all the answers

What is a unique property of hydrous lanolin?

It has a cooling effect upon skin application. Signup and view all the answers

Study Notes

Pharmaceutics 3 - 2020

Course taught by Dr. Noha Younis
Focuses on ointments, types, classification, and characteristics of an ideal ointment

Chapter One - Ointments

Definition: A homogeneous, viscous semisolid preparation, commonly greasy and oily (Oil-80%, Water-20%). Intended for external application to skin or mucous membranes. Used as emollients, protective, therapeutic or prophylactic agents.
Types of Ointment:
- Medicated ointment: Contains an active pharmaceutical ingredient (API) for protective, therapeutic or prophylactic purposes.
- Non-medicated ointment: Used for physical effects like protection (barrier), emollients or lubricants.
Classification of ointments according to place of action:
- Epidermic: Acts on the epidermis (outer skin layer).
- Endodermic: Acts on deeper layers of cutaneous tissues (penetrates into skin).
- Diadermic: Penetrates deep to release medicaments into body fluids, like systemic circulation.
Characteristics of an ideal ointment:
- Physically and chemically stable.
- Finely divided active ingredients uniformly distributed, smooth and free from grittiness.
- Inert, odorless base.
- Low irritation and sensitization index.
- Should not retard wound healing.
- Should melt at body temperature for efficient medicament release.
- Compatible with common medicaments and skin.
- Easily washable with water.
- Economical and easy to transport.
Advantages of ointments:
- Site-specific action with fewer side effects.
- Avoids first-pass metabolism.
- Convenient for unconscious patients.
- Chemically more stable and easier to handle compared to liquid dosage forms.
- Suitable dosage forms for bitter-tasting drugs.
Disadvantages of ointments:
- Staining and cosmetically less aesthetic.
- Application with fingertip may contaminate the formulation or cause irritation.
- Bulkier to handle compared to solid dosage forms.
- Dose accuracy is determined by the quantity applied.
- Physio-chemically less stable than solid dosage forms.

Types of Ointment Bases

Oleaginous ointment base (hydrocarbon base, water in oil):
- A choice of base for dry, chapped skin.
- Examples:
  - Petrolatum (Soft paraffin):
    - Pale yellow, odorless; melting point 38-56°C (yellow)
    - White, odorless, melting point 38-56°C (white) -Suitable for epidermal preparations.
  - Hard paraffin: Solid from hydrocarbon obtained from petroleum; colorless or white, odorless mass. Used to harden or stiffen ointments.
Absorption ointment bases (water in oil):
- Hydrophilic/absorbent
- Examples: -Anhydrous lanolin (wool fat): Non-soluble in water but absorbs a large amount of water
Water removable (water washable base):/water soluble base:
- Emulsifying bases (oil in water).
- Examples: Polyethylene glycol polymers (PEG) - water soluble, non-volatile, inert, not hydrolysis, not support the bacterial growth or mold growth.
Other bases:
- Animal fats and plant fats (spermaceti, carnauba wax)

Methods of Preparation of Ointment

Incorporation (trituration):
- Used for insoluble substances.
- Levigate insoluble substance with base until smooth.
- Incorporate into remainder of the base.
- Water-soluble salts may be dissolved in small quantities of water and then incorporated into base.
- Fusion may be used if high melting point ingredient will be incorporated in a molten base then all the other ingredients added, mixed and stirred to have uniformity
Fusion: Ingredients melted together in descending order of their melting points to ensure homogeneity.

Evaluation Parameters of Ointments

Physical methods: Rate of absorption, non-irritancy, rate of penetration, rate of drug release, rheological properties, content uniformity
Microbiological methods: Test of microbial content, test of preservative efficacy.

Ophthalmic Ointments

Sterile, homogeneous, semi-solid preparations for eye application.
Prepared from non-aqueous bases (e.g. soft paraffin, liquid paraffin, wool fat).
May contain additives like antimicrobial agents, antioxidants, and stabilizing agents.
Materials must be impalpable to prevent eye discomfort.
Advantages: Longer contact time, flexibility in drug choice, improved drug stability and storage stability.
Disadvantages: Sticking of eyelids, blurred vision, poor patient compliance, interfere with corneal epithelial cell attachment, matting of eyelids.

Creams

Semisolid dosage form containing one or more drug substances dissolved or dispersed in a suitable base.
- Lighter than ointments
Formulated for application to skin or mucous membranes, especially when occlusive effect is not necessary.
Two main types: Oil-in-water (O/W) and water-in-oil (W/O).
O/W creams: Water washable, causes rapid absorption and penetration, thin, white, smooth consistency, cosmetically acceptable, and easily washed off with water..
W/O creams: Creamy, white or translucent; more difficult to handle, but drugs are more readily released from W/O than O/W.
Properties of creams: rapid absorption and penetration, thin, white, smooth consistency, more comfortable and cosmetically acceptable. More easily washed off usage.

Pastes

Semisolid preparations with high percentage of insoluble particulate solids (often > 50%).
Thicker and stiffer than ointments.
Used as protective barriers, absorb and neutralize harmful chemicals and protect skin lesions.
Examples of insoluble ingredients include starch, zinc oxide and calcium carbonate.

Liniments

Alcoholic or oleaginous solutions or emulsions of medicinal substances.
Used for rubefacient and counterirritant effects.
Oily liniments often function as protective coatings.
Applied with rubbing to affected area.

Colloidions

Liquid preparations containing pyroxylin (nitrocellulose) in a mixture of ethyl ether and ethanol.
Applied with a soft brush to form a thin film of pyroxylin.
Used for external application.

Glycerites

Solutions or mixtures of medicinal substances in 50% or higher concentration of glycerin.
Useful as pharmaceutical solvents and for concentrated solutions.
Hygroscopic, stored in tightly closed containers.
Used for topical administration.

Suppositories

Semisolid or solid dosage form intended to be inserted into body cavities (rectum, urethra, vagina).
Melt or soften at body temperature to release the drug.
All types of suppositories melt at normal body temperature after introducing in body cavity and produce their effect.
Advantages: alternated route of administration; suitable for unconscious patients; suitable for drugs with bad odor and taste.
Types: Rectal, urethral, vaginal, nasal, or ear cones; different shapes and sizes according to body cavity for insertion.
Ideal properties: solid form at room temperature, not irritate, stable in storage, no change in appearance, colour, or odour., retain hardness, and shape when handled, not stick to mould, melt at body temperature, release drug rapidly, do not react with drugs or additives.
Base types: hydrophilic (glycero-gelatin) and lipophilic (cocoa butter).
- Hydrophilic bases are better suited for mixtures of water and other materials.
- Lipophilic bases are better suited for mixtures of oils.

Powders

Fine state of division of solid drugs, for internal or external use. -Advantages: good chemical stability, useful for bulky drugs, easy to swallow, rapid dissolution in fluids, less incompatibility, easier to carry. -Disadvantages: not suitable for drugs unstable in atmospheric conditions, bitter or irritating drugs, inaccurate doses in bulk powders. -Types: divided powders (packets), bulk powders (cardboard, glass, or plastic containers-usually non-potent drugs), dusting powders (superficial application to skin), insufflations (inhalation into cavities), snuffs (inhalation into nasal passages), dentifrices (tooth powders).
Challenges include hygroscopic or deliquescent powders, effervescent problems, incorporation of liquids or extracts and explosive mixtures
Preparation Methods: Wet granulation, dry granulation, direct compression, methods of granulation.

Capsules

Solid dosage forms containing one or more drugs enclosed in a gelatin shell, for internal use.

Tablets

Solid dosage forms prepared usually by compression of powdered drug and excipients.
Advantages: compact, easy to swallow, better patient compliance, lower cost, no need for measuring precise doses.
Disadvantages: poor dissolution profile, difficult for children/elderly to swallow, stability problems in some drugs.

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Description

Test your knowledge on polymorphism and crystallization processes in pharmaceuticals. This quiz covers various aspects including factors affecting polymorphism, methods of supersaturation, and best practices in formulation. Perfect for students and professionals in the field of pharmacy and materials science.