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Which of the following substances would likely form a eutectic mixture?
Which of the following substances would likely form a eutectic mixture?
What effect occurs when a drug is added to a poorly soluble solvent?
What effect occurs when a drug is added to a poorly soluble solvent?
What is the definition of stability according to USP?
What is the definition of stability according to USP?
Which temperature indicates a polymorphic form of Cocoa Butter that should not be exceeded?
Which temperature indicates a polymorphic form of Cocoa Butter that should not be exceeded?
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Which of the following is a responsibility of pharmacists regarding product stability?
Which of the following is a responsibility of pharmacists regarding product stability?
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In chemical kinetics, the rate of reaction can be described as proportional to what?
In chemical kinetics, the rate of reaction can be described as proportional to what?
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What is the rate equation in a generalized chemical reaction aA + bB = Products?
What is the rate equation in a generalized chemical reaction aA + bB = Products?
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What happens to chlorpromazine base if its concentration exceeds its water solubility when the pH is raised?
What happens to chlorpromazine base if its concentration exceeds its water solubility when the pH is raised?
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Which statement about digoxin's solubility is accurate?
Which statement about digoxin's solubility is accurate?
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Why is refrigeration recommended for certain drug solutions?
Why is refrigeration recommended for certain drug solutions?
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What are common factors that affect the rates of reaction in chemical kinetics?
What are common factors that affect the rates of reaction in chemical kinetics?
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What characteristic defines efflorescent powders?
What characteristic defines efflorescent powders?
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What distinguishes deliquescent powders from hygroscopic ones?
What distinguishes deliquescent powders from hygroscopic ones?
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Why is it important to heat Cocoa Butter slowly and not exceed 340°C?
Why is it important to heat Cocoa Butter slowly and not exceed 340°C?
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Which of the following drugs should not be refrigerated due to precipitation effects?
Which of the following drugs should not be refrigerated due to precipitation effects?
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Which of the following accurately defines hygroscopic drugs?
Which of the following accurately defines hygroscopic drugs?
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What is the formula for calculating the zero order rate constant?
What is the formula for calculating the zero order rate constant?
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What keeps the concentration of a drug in a zero order suspension relatively constant?
What keeps the concentration of a drug in a zero order suspension relatively constant?
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In a first order reaction, how is the rate of change of concentration expressed?
In a first order reaction, how is the rate of change of concentration expressed?
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For a liquid aspirin preparation containing 6.5 g in 100 ml, what is the maximum concentration left after it has decomposed to 90% of its original concentration?
For a liquid aspirin preparation containing 6.5 g in 100 ml, what is the maximum concentration left after it has decomposed to 90% of its original concentration?
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What is the calculated shelf life of the aspirin suspension at 250C?
What is the calculated shelf life of the aspirin suspension at 250C?
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Which of the following is true regarding the integration of a first order reaction?
Which of the following is true regarding the integration of a first order reaction?
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What unit is used for the zero order rate constant in this context?
What unit is used for the zero order rate constant in this context?
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What does the equation C = C0 - kt represent in the context of drug concentration?
What does the equation C = C0 - kt represent in the context of drug concentration?
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What is the overall order of the reaction between ethyl acetate and sodium hydroxide?
What is the overall order of the reaction between ethyl acetate and sodium hydroxide?
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What does the rate constant k represent in a reaction?
What does the rate constant k represent in a reaction?
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In the context of pseudo first order reactions, which statement is true?
In the context of pseudo first order reactions, which statement is true?
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What is the unit of the rate constant k for a second order reaction?
What is the unit of the rate constant k for a second order reaction?
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How does the concentration change in zero order reactions?
How does the concentration change in zero order reactions?
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What is the half-life in the context of zero order reactions?
What is the half-life in the context of zero order reactions?
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Which of the following statements accurately describes the integration of zero order reaction rate equations?
Which of the following statements accurately describes the integration of zero order reaction rate equations?
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If a reaction is first order with respect to ethyl acetate and sodium hydroxide, what will happen if the concentration of sodium hydroxide is significantly increased?
If a reaction is first order with respect to ethyl acetate and sodium hydroxide, what will happen if the concentration of sodium hydroxide is significantly increased?
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What is the formula for calculating the half-life of a first order reaction?
What is the formula for calculating the half-life of a first order reaction?
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In the context of a first order reaction, what does 'k' represent?
In the context of a first order reaction, what does 'k' represent?
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For a substance in a first order reaction that starts with an initial concentration of 500 units/ml and is measured at 300 units/ml after 40 days, what is the rate constant 'k'?
For a substance in a first order reaction that starts with an initial concentration of 500 units/ml and is measured at 300 units/ml after 40 days, what is the rate constant 'k'?
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If the half-life of a first order reaction is determined to be 54.3 days, what will be the concentration of the drug after one half-life if the initial concentration was 500 units/ml?
If the half-life of a first order reaction is determined to be 54.3 days, what will be the concentration of the drug after one half-life if the initial concentration was 500 units/ml?
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What type of reactions typically involve bimolecular reactions where two reactants combine?
What type of reactions typically involve bimolecular reactions where two reactants combine?
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For second order reactions, what does the integration for calculating 'k' include?
For second order reactions, what does the integration for calculating 'k' include?
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In a second order reaction with equal initial concentrations of A and B, how is the half-life expressed?
In a second order reaction with equal initial concentrations of A and B, how is the half-life expressed?
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What method can be used to determine the order of a reaction based on concentration versus time?
What method can be used to determine the order of a reaction based on concentration versus time?
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Study Notes
Stability in Pharmaceutics
- Definition of stability: A product retains its properties within specified limits throughout its storage and use period.
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Pharmacist's responsibilities:
- Adhering to expiration dates and rotating stock
- Observing products for signs of instability
- Proper handling of extemporaneously prepared drugs
- Using recommended containers and closures
- Educating patients about storage and use
Examples of Instability
- Chlorpromazine: An increase in pH of an aqueous solution can convert the soluble hydrochloride salt to the insoluble base.
- Temperature effects: Solubility of most drugs decreases with lower temperature. Refrigeration may retard degradation, but can cause precipitation.
- Efflorescent powders: Powders containing water of hydration can release moisture during trituration or low humidity.
- Hygroscopic and Deliquescent powders: These powders absorb moisture from the air. Deliquescent powders absorb enough moisture to dissolve and form a solution.
- Eutectic mixtures: Two or more substances that liquefy when mixed at room temperature.
- Solvent effects: Adding a solvent in which the drug is poorly soluble to a solution can cause precipitation.
- Polymorphic conversions: Drugs can exist in various crystalline structures, impacting their properties.
Chemical Kinetics
- Rate of reaction: The speed at which a reaction occurs, often expressed as the change in concentration over time.
- Law of Mass Action: The rate of a reaction is proportional to the product of the molar concentrations of the reactants raised to their respective powers.
- Rate constant (k): A proportionality constant that quantifies the rate of a reaction.
- Order of reaction: The sum of the powers to which the concentrations of reactants are raised in the rate equation.
- Pseudo first-order reaction: A reaction that appears first order because the concentration of one reactant is in vast excess and changes negligibly.
Types of Reactions
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Zero-order reactions: The rate of reaction is independent of the concentration of the reactant(s).
- Example: Loss of color of a drug. Half-life: t1/2 = 0.5A0/k0
- Apparent zero-order: Suspensions, where the drug in solution stays relatively constant as more is released from the suspended particles.
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First-order reactions: The rate of reaction is directly proportional to the concentration of the reactant.
- Example: Decomposition of a drug. Half-life: t1/2 = 0.693/k
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Second-order reactions: The rate of reaction is proportional to the square of the concentration of the reactant.
- Example: Bimolecular reactions.
Determination of Reaction Order
- Substitution method: Test data in equations for different orders to determine the best fit.
- Graphic method: Plot concentration vs time for different orders (zero-order: straight line, first-order: logarithmic).
- Half-life method: Calculate half-lives at different concentrations and use the relationship between half-life and order.
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Description
This quiz explores the concept of stability in pharmaceutics, defining its significance in maintaining product properties during storage and use. It covers the responsibilities of pharmacists regarding expiration dates, signs of instability, and proper handling of drugs. Additionally, examples of various instabilities are reviewed to understand their implications on pharmaceutical products.
