Podcast
Questions and Answers
What factor increases the stability of a drug within a micellar system?
What factor increases the stability of a drug within a micellar system?
- Entrapment in the lipophilic micellar core (correct)
- Positioning near the micellar surface
- Increased ionic strength of the solvent
- Using a non-ionic surfactant
How does the ionic nature of the surfactant affect drug stability?
How does the ionic nature of the surfactant affect drug stability?
- Non-ionic surfactants have no effect on drug stability
- Cationic surfactants increase instability in a base-catalyzed environment (correct)
- Anionic surfactants mitigate drug hydrolysis by neutralizing charges
- All surfactants enhance drug stability regardless of the environment
What is the primary salt effect related to ionic strength in a drug solution?
What is the primary salt effect related to ionic strength in a drug solution?
- Direct chemical interaction between electrolyte and drug
- Increase of drug solubility via ion pairing
- Alteration of the reaction rate without direct interaction (correct)
- Decrease in the molar concentration of the drug
In the reaction expressed as AZA + BZB → (A-----B)(ZA+ZB), what variable controls the reaction rate?
In the reaction expressed as AZA + BZB → (A-----B)(ZA+ZB), what variable controls the reaction rate?
According to the rate equation log k = log ko + 1.02ZAZB√μ, what does 'μ' represent?
According to the rate equation log k = log ko + 1.02ZAZB√μ, what does 'μ' represent?
What is the significance of the term 'Z' in the context of the reaction between ions?
What is the significance of the term 'Z' in the context of the reaction between ions?
Which of the following is NOT a characteristic of chemical incompatibilities?
Which of the following is NOT a characteristic of chemical incompatibilities?
Which statement describes the effect of increases in ionic strength on drug stability?
Which statement describes the effect of increases in ionic strength on drug stability?
In scenarios where a drug is hydrolyzed by base, which surfactant type would be most detrimental to stability?
In scenarios where a drug is hydrolyzed by base, which surfactant type would be most detrimental to stability?
Which of the following factors does not directly relate to storage conditions affecting drug stability?
Which of the following factors does not directly relate to storage conditions affecting drug stability?
What effect does the addition of buffers have on the pH of a drug solution?
What effect does the addition of buffers have on the pH of a drug solution?
Which of the following statements about hydrolysis catalysis is incorrect?
Which of the following statements about hydrolysis catalysis is incorrect?
When determining the optimum pH for drug stability, what approach is usually taken?
When determining the optimum pH for drug stability, what approach is usually taken?
In drug formulation, weak basic drugs like Pilocarpine demonstrated stability under which conditions?
In drug formulation, weak basic drugs like Pilocarpine demonstrated stability under which conditions?
Which of the following is not a solution-related factor affecting drug stability?
Which of the following is not a solution-related factor affecting drug stability?
What is the primary reason for evaluating decomposition reaction rates across different pH values?
What is the primary reason for evaluating decomposition reaction rates across different pH values?
Which of the following enhances the reaction rate of hydrolysis in buffers?
Which of the following enhances the reaction rate of hydrolysis in buffers?
Which factor does not influence drug stability through solution properties?
Which factor does not influence drug stability through solution properties?
What role do surfactants play in drug stability?
What role do surfactants play in drug stability?
What primarily differentiates homogeneous catalysis from heterogeneous catalysis?
What primarily differentiates homogeneous catalysis from heterogeneous catalysis?
In what way does specific acid-base catalysis differ from general acid-base catalysis?
In what way does specific acid-base catalysis differ from general acid-base catalysis?
Which factor does NOT influence the solvent effect on the reaction rate?
Which factor does NOT influence the solvent effect on the reaction rate?
What is the primary role of a catalyst in a chemical reaction?
What is the primary role of a catalyst in a chemical reaction?
What does the micellar constant (Km) indicate in the context of surfactants and drug stability?
What does the micellar constant (Km) indicate in the context of surfactants and drug stability?
Which of these statements about the role of a catalyst is accurate?
Which of these statements about the role of a catalyst is accurate?
Which of the following conditions is least likely to affect drug hydrolysis in the presence of surfactants?
Which of the following conditions is least likely to affect drug hydrolysis in the presence of surfactants?
What is true regarding the effect of solvent polarity on reactions with neutral reactants?
What is true regarding the effect of solvent polarity on reactions with neutral reactants?
Which of the following describes a characteristic of heterogeneous catalysis?
Which of the following describes a characteristic of heterogeneous catalysis?
Flashcards
Hydrolysis
Hydrolysis
The process of a drug breaking down into smaller molecules, usually due to reaction with water.
Buffer
Buffer
A substance that resists changes in pH, helping to maintain a stable drug solution.
Decomposition Rate
Decomposition Rate
The speed at which a drug decomposes. A faster rate means the drug breaks down quicker.
Optimum pH
Optimum pH
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Buffer Selection
Buffer Selection
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pH-rate Profile
pH-rate Profile
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Storage Conditions
Storage Conditions
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Catalysts
Catalysts
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Dielectric Constant
Dielectric Constant
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Surfactants
Surfactants
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Homogeneous catalysis
Homogeneous catalysis
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Heterogeneous catalysis
Heterogeneous catalysis
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Specific acid-base catalysis
Specific acid-base catalysis
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General acid-base catalysis
General acid-base catalysis
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Solvent effect
Solvent effect
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Micellar constant (Km)
Micellar constant (Km)
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Drug stability in micelles
Drug stability in micelles
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Ionic Strength (μ)
Ionic Strength (μ)
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Primary Salt Effect
Primary Salt Effect
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Rate of Reaction
Rate of Reaction
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Rate Constant at Infinite Dilution (ko)
Rate Constant at Infinite Dilution (ko)
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Specific Rate Constant (k)
Specific Rate Constant (k)
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Lipophilic Micellar Core
Lipophilic Micellar Core
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Micellar Surface
Micellar Surface
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Micellar Protection
Micellar Protection
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Study Notes
Factors Affecting Drug Stability
- Drug stability is influenced by various factors, categorized as storage conditions and solution-related factors.
Storage Conditions-Related Factors
- Temperature: Affects drug stability.
- Humidity: Affects drug stability.
- Oxygen: Affects drug stability.
- Light: Affects drug stability.
Solution-Related Factors
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pH (Buffers): Hydrolysis is affected by the pH of the drug solution. Specific acid or base catalysis occur faster in acidic or basic media, respectively, compared to neutral media. General acid-base catalysis occurs faster in buffered solutions than non-buffered solutions.
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Optimum pH: To determine the optimal pH for drug stability during formulation, various pH values are tested and a pH-rate profile is plotted. The plot identifies the pH at which the drug solution exhibits maximum stability.
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Catalyst: A substance that accelerates a chemical reaction without being consumed in the process.
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Homogenous Catalysis: Catalyst and reactants are in the same phase.
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Heterogenous Catalysis: Catalyst and reactants are in different phases, often involving solid catalysts in liquid reaction mixtures.
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Specific Acid-Base Catalysis: This reaction is affected only by the concentration of H+ or OH- ions. It's divided into specific acid and specific base catalysis. The general acid-base catalysis reaction rate isn't just dependent on the pH of the solution but also the type of weak acid used. A catalyst in this context could be fine solid particles, like platinum, or the walls of the container.
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Solvent (Dielectric Constant = Polarity): The solvent's polarity affects drug reaction rates, but only with charged reactants. Neutral reactants are unaffected by solvent polarity.
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Surfactant: Entrapment of drugs into micelles improves stability against hydrolysis. Polarity of drugs impact how stable they are within a micelle and drugs are more protected within the lipophilic core compared to near the surface. Positively or negatively charged surfactants influence drug stability, with opposing charges leading to instability.
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Ionic strength (μ): Represents the concentration of ions in a solution. Adding inert electrolytes to a drug solution affects its stability without changing the drug-electrolyte interaction, creating a 'primary salt effect.' The rate equation for ionic reactions depends on ionic strength, differing at infinite dilution (μ = 0).
Mechanisms of Drug Incompatibilities
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Chemical Incompatibilities: Chemical interactions between two or more drug components within a dosage form, or between a drug and an excipient (e.g., between a drug or excipient with an amine functional group).
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Drug-Drug Interactions: Inactivation of cationic aminoglycoside antibiotics (like kanamycin, gentamicin) by anionic penicillins in IV mixtures. Anionic heparin and aminoglycoside antibiotics also form inactive complexes. Other drug-drug incompatibilities cause drug precipitation (e.g., epinephrine sulfate and steroid sodium phosphate, eye drops containing polymyxin B sulfate and dexamethasone sodium phosphate).
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Drug-Excipient Interactions: Aminophylline and glucose form Schiff's base (yellow ppt). Phenolic drugs (phenobarbital) and acidic drugs (aspirin) can react by hydrogen bonding, e.g. with Tween 80, leading to ester formation.
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Types of in vitro interactions:
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drug-drug interaction
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drug-excipient interaction
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drug-packaging material interaction
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other interactions
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Description
This quiz explores the various factors that influence drug stability, focusing on both storage conditions and solution-related factors. Key elements include temperature, humidity, oxygen exposure, light, and the impacts of pH and catalysts on drug formulations. Test your knowledge on how these factors play a role in maintaining drug efficacy.
