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Questions and Answers
What is the correct method to calculate 90% of a concentration of 1.2 mg/mL?
What factors determine the mechanism of a chemical reaction according to collision theory?
How does pH influence the reaction rate in drug stability?
What does accelerated stability testing aim to achieve?
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What is the specific rate constant (k) of a drug at 25°C if it is given as 3 x 10^-5 h-1?
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If a drug has an initial concentration of 200 mg/mL and a limit of viability at 150 mg/mL, what does this imply?
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After how much time will a drug with an initial concentration of 3.2 mg/mL and a stability constant k of 0.05 mg/mL/h decompose by 10%?
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Which of the following factors can increase the decomposition of drugs by hydrolysis?
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What does the negative sign in the degradation reaction's rate of change indicate?
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What is the order of the reaction if the degradation of the drug molecule is represented as second order?
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In a zero-order reaction, what is true about the rate of the reaction?
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If the initial drug concentration, [D]0, is 200 mg/mL and the rate constant, k0, is 0.380 (mg/mL∙days-1), how long will it take to decrease by 50%?
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How is the slope related to the rate constant in a zero-order reaction?
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What can be compared using the rate constants, k, from different drug degradation reactions?
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Which statement is NOT true regarding zero-order reactions?
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What does the variable 'k2' represent in the degradation process?
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What is the primary reaction mechanism for drug degradation involving water as a solvent?
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Which order of reaction typically describes a scenario where the reaction rate is constant and independent of the concentration of the reactants?
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How does the shelf-life of a drug product primarily get established?
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What duration does the half-life of a drug specifically refer to?
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What is the purpose of stability testing for pharmaceuticals?
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Which of the following factors is NOT typically considered in stability testing protocols?
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In a first-order reaction, how is the rate of reaction related to the concentration of the reactant?
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What does pseudo reaction order describe in the context of drug stability?
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What is meant by the expiration date of a pharmaceutical product?
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What does stability mean in the context of pharmaceuticals?
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What is the primary type of solvolysis reaction relevant to pharmaceuticals?
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Which functional groups are major targets for hydrolysis?
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What effect does pH have on oxidation reactions?
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What is a common result of hydrolysis in stored pharmaceuticals?
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Which of the following methods can minimize oxidation in pharmaceutical products?
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What role do chelating agents play in pharmaceutical stability?
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In the provided reaction, what is the stoichiometric ratio of N2O5 to NO2?
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How is the reaction order determined in the provided rate law for first order?
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What is the impact of high humidity on the storage of pharmaceuticals?
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What is a characteristic of oxidation reactions in pharmaceuticals?
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What is the relationship between the rate of a first order reaction and the concentration of reactants?
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What is the equation for the half-life of a first order reaction represented as?
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How is shelf-life defined in the context of drug stability?
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If a drug has an initial concentration of 500 units/mL and is found at 300 units/mL after 40 days for a first order reaction, what is the next concentration level to achieve before reaching half-life?
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What is the purpose of conducting stability studies on drug products?
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What does the degradation constant 'k' indicate in the context of a first order reaction?
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When 90% of a drug has decomposed in a first order reaction starting with 1.2 mg/mL, what calculation shows the remaining concentration?
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In the context of zero and first order reactions, which of the following describes a key difference?
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Study Notes
Chemical Kinetics
- Chemical kinetics studies the rates of chemical reactions.
- Reaction rates depend on reactant concentrations.
- Reaction rate is expressed as a change in concentration over time (M/s).
- Rate = change in [reactant] / change in time.
Learning Objectives
- Apply reaction rate and order calculations to drug stability.
- Discuss pseudo reaction order.
- Calculate half-life and shelf-life of pharmaceutical products.
- Discuss stability testing protocols and regulatory requirements.
Outline
- Common Drug Degradation Reactions:
- Hydrolysis
- Oxidation
- Photolysis
- Order of Reaction:
- Zero-order reactions
- First-order reactions
- Pseudo-order reactions
- Stability and Shelf Life of Drugs:
- Factors influencing stability
- Accelerated stability testing
- Enzyme Catalysis Reactions
- Pharmacokinetics:
- Zero-order absorption
- First-order absorption
- Radioactivity
Common Drug Degradation Reactions
- Solvolysis (Hydrolysis): Focus on solvolysis and oxidation, hydrolysis is the primary solvolysis reaction.
- Oxidation: While oxygen is not required for an oxidation reaction, oxygen is the primary oxidizing agent for most pharmaceutical degradation reactions.
- Photolysis: Focus on solvolysis and oxidation, hydrolysis is primary solvolysis reaction.
Relevant Terms
- Chemical Kinetics: Deals with drug stability and their degradation through reaction rates and mechanisms.
- Stability: The ability of a drug to maintain chemical, physical, microbiological, and biopharmaceutical properties within specified limits throughout its shelf-life.
- Stability Tests: A series of tests designed to assess a drug's stability to determine shelf-life and utilization period under specified conditions.
-
Shelf Life: Expiration Dating Period or Validity Period.
- The time a drug product can be expected to retain within its specifications if stored correctly.
- Shelf-life is determined from stability studies.
- Shelf-life is used to establish an expiry date for batches of a drug product.
- Represents the time needed for 10% material disappearance (A decreasing to 90%).
- Expiration Date: The date placed on a drug product's container, signifying when a batch is no longer usable even under ideal conditions.
- Half-Life: The time required for half of the material to disappear (A decreasing to 1/2A).
Stability Testing
- To determine how a drug substance or product changes over time due to environmental factors (temperature, humidity, light).
- To establish a retest period or shelf-life and recommend optimal storage conditions.
Reaction Rates
- Reaction Rate: The rate of change in concentration of a reactant or product over time (M/s).
- Rate: change in number of moles of B / change in time = Δ[B] / Δt
- Reactants decrease with time, products increase with time.
Order of Reactions
- Understanding reaction rates, order, and rate constants aids pharmacists in determining beyond-use dates, maintaining storage conditions, and developing stable products.
- Determining reaction order using mathematical analysis of the degradation process.
- Mass degradation reaction can be described as: D + W → Degradation Products
Pseudo Reactions
- Many drug degradation reactions involve water as a reactant, where water's concentration is much higher than the drug, thus considered fairly constant.
- -d[D]/dt = k₂[D][W]
- If [W] is constant: k₁ = k₂[W]
- -d[D]/dt = k₁ [D]
Zero-Order Reactions
- Reaction rate is independent of the reactant concentrations.
- Rate is determined by a constant decrease in the drug concentration ([D]).
- Rate = k₀
- [D]t = [D]₀ - k₀t
- Half-life = [D]₀ / 2k₀
First-Order Reactions
- Rate is directly proportional to the concentration of one reactant.
- Rate = k[D]
- ln[D]t = ln[D]₀ – kt
- Half-life = 0.693 / k
Accelerated Stability Testing
- Various stress conditions are applied to drugs to speed up the decomposition process.
- Temperature increases reaction rate
- Humidity increases decomposition via hydrolysis
- Light increases effect of daylight.
- These tests are used to predict long-term stability.
- Storage conditions are described using specifications like temperature, relative humidity.
Expiration Date Calculation
- Formulas for calculating expiration dates depend on the order of the degradation reaction (e.g., zero-order or first-order).
Effects of pH
- The magnitude of reaction rates catalyzed by H⁺ and OH⁻ ions can vary depending on pH.
- pH of optimum stability is determined by plotting log k against pH.
- Acidic catalysis occurring at lower pH
- Basic catalysis occurring at higher pH
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Description
Explore the principles of chemical kinetics and their application to drug stability. This quiz covers reaction rates, order of reactions, and factors influencing the shelf life of pharmaceuticals. Understand the significance of hydrolysis, oxidation, and stability testing protocols in the context of drug degradation.
