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Worksheetspharmaceutics exam 3
Total questions: 44
Worksheet time: 26mins
the degradation of a poorly water soluble drug follows first order kinetic. it has been formulated in a suspension form. which of the following statements is/are correct about the degradation profile of the drug formulated as suspension.
at the beginning degradation of the drug would follow zero order but after sufficient long time period it would be 1st order only when all of the suspended drug has got dissolved.
at the beginning degradation of the drug would follow 1st order but after sufficient long time period it would be zero order only when all of the suspended drug has got dissolved.
neither
What is the remaining concentration (a) in mg/ml of a drug (initial concentration, a=7mg/ml) after a time equivalent to 3 half-lives assuming that the decomposition follows first-order kinetics?
0.875
1.167
3.5
1.75
the time taken for 5% of a drug to decompose by first-order kinetics is
0.105/k1
k1/0.05
0.022/k1
0.051/k1
the following data were obtained for the hydrolysis of homatropin (which follows first order kinetics) in 0.226 mol/L HCl at 90C. calculate the rate constant.
0.53 hr-1
5.3 hr-1
5.25 hr-1
0.053 hr-1
In a zero order reaction
the half life is equal to 0.693/k
the unit of k is concentration /time
a plot of the amount remaining (as ordinate) against time (abscissa) is linear with a slope 1/k
none
Lineweaver-burke equation for an enzymatic reaction is useful for
determining the constant Km in michaelis menton equation
determining the constant Vmax in michaelis equation
determining only the constant Km or Vmax but not both simultaneously in michaelis menton equation
none
In a zero order reaction
The rate of decomposition is dependent on the concentration of one of the reactants
The rate of decomposition is independent on the concentration of any of the reactants
A plot of the amount remaining (as ordinate) against time (abscissa) is linear with a slope 1/k
none
The hydrolytic degradation of acetylsalicylic acid in its aqueous suspension follows which kind of kinetic?
second order
pseudo zero-order
first order
zero order
In a zero order reaction, the rate of decomposition is dependent of the concentration of one of the reactants
true
false
The driving force for processes to occur is
all systems spontaneously move towards lower free energy (chemical potentials) and higher entropy
all systems spontaneously move towards lower free energy (chemical potentials) and lower entropy
neither
It is conceivable for a reaction to have zero or fractional molecularity
true
false
In a second order reaction
the rate of reaction depends on the concentration of two reacting species
a plot of time (as abscissa) against (ao-a)/(aao) (as ordinate) in linear with a slope equal to 1/k2
the half-life is independent of concentration
the unit of k is concentration/time
none
Which of the following is not a characteristic of a solid state reaction
It happens in a homogenous medium
It involves initiation as a pre-reaction step
It involves induction as a pre-reaction step
In involves nucleation before the propagation of the reaction
A base catalyzed hydrolysis of an ester such as chloramphenicol palitate can exhibit
a second-order kinetics only if the concentration of both - ester and base are changing
a pseudo first-order kinetics if the concentration of they hydroxyl ion is maintained constant
a pseudo zero-order kinetics if the concentration of both ester and base are maintained constant
a first-order kinetics if the concentration of the hydroxyl ion is maintained constant
a zero-order kinetics if the concentration of both ester and base are maintained constant
Select the correct order of degradation of a drug by hydrolysis
pseudo first-order
first order
zero order
second order
It is not conceivable for a reaction to have zero or fractional molecularity
true
false
In a study of the hydrolysis of a drug in aqueous solution a plot of logarithm of the amount of the drug remaining (as ordinate) against time (abscissa) is linear.
the reaction is zero order
the slope is -2.303/k
the unit of k is concentration-1time-1
the half-life does not depend on the initial concentration of reactant.
Prout-Tompkins Model best describes
A gaseous state reaction
A solid state reaction
A meta-phase reaction
A liquid state reaction
For a single step (elementary) reaction, the molecularity and order are the same
true
false
The rate or speed of a process (a physical or chemical change) can be defined by
the rate at which the concentration of a species undergoing the change decreases
the rate at which the concentration of the resulting species increases with time
the rate at which the concentration of the resulting species decreases with time
The half-life of a drug in a solution is 30min. What would be the concentration of the drug in the solution after 90min?
12.5% of the initial concentration
75% of the initial concentration
50% of the initial concentration
25% of the initial concentration
reaction of a drug with oxidation is minimized by
proper selection of packaging material
proper selection of polymer used for film coating over the tablet
removal of oxygen over the surface of the drug in a package
reduction in the particle size of a drug in a solid dosage form results in its faster dissolution.
yes because reduction in size results in decrease in surface area
yes because reduction in size results in increase in surface area
the above statement is incorrect because rate of dissolution, in fact, decrease with decrease in particle size of the drug
The initial concentration of active principle in an aqueous preparation was 5x10-3 g/mL. After 10 months the concentration was found to be 4.2x10-3 g/mL. The drug is known to be ineffective after it has decomposed to 70% of its original concentration. Assuming that decomposition follows first order kinetics, calculate the expiry date of the drug preparation.
4.9months
20.5 months
40 months
40.9 months
The rate of dissolution when surface area exposed to the solvent/medium remains the same is called
General dissolution rate
Specific dissolution rate
Intrinsic dissolution rate
Non-specific dissolution rate
Following are the steps involved in the process of determining self-life or expiration date of a drug
Reaction rate constant, k, is determined at various elevated temperatures
A plot of log k vs 1/T will be a straight line which can provide the value of k at room temperature
neither
Initial burst release is observed for which of the following matrix-based controlled drug release system
Reservoir-based sustained release system
Osmotic pump-based drug release system
Insoluble matrix systems
Hydrophilic or swellable matrix systems
Which is not a variable in the noyes and whitney equation
pH
Mass rate of dissolution
Thickness of diffusion layer
Surface area of solid
Sodium salicylate is capable of _____ at the diffusion layer and displays a greater rate of dissolution under conditions of more acidic simulated gastric fluid than salicylic acid
Supersaturation
Sinking
Diffusion
Complexation
Amber colored glass container is used to prevent the drug from
Hydrolysis
Esterification
Photolysis
Deamidation
The rate of general acid- and base-catalysis is affected by concentration of undissociated buffer components in addition to hydronium and hydroxyl ion concentration
true
false
The release of a drug from a matrix system occurs by
Diffusion from the matrix system
Erosion of the matrix system
neither
Which of the following equations predicts the stability of a drug at room temperature from experiments at accelerated condition at higher temperatures?
Stokes equation
Ideal gas equation
Arrhenius equation
Michaelis-menton equation
The plasma level of an orally administered tabled depends on
The rate of tablet disintegration
The rate of dissolution of the drug
neither
Hydrogen peroxide is stored in a dark container to prevent it from
Deamidation
Photolysis
Esterification
Hydrolysis
An increase in temperature by 10C near room temperature is known to cause
Only 2 fold increase in reaction rate for many reactions
A 2-4 fold increase in reaction rate for many reactions
A 2-4 fold increase in reaction rate for a few rare reactions
A 2-4 fold decrease in reaction rate for many reactions
Dissolution rate can be increased by
Decreasing solubility
Decreasing diffusion coefficient
Increasing thickness of the diffusion layer
Increasing diffusion coefficient
Insoluble polymers such as ethyl cellulose, methylmethacrylate, or polyvinyl acetate are used for making inert matrix-based extended drug release systems
true
false
Following are some approaches to prevent the oxidative degradation of drug
using an initiation inhibitor such as EDTA (ethylene diamine tetraacetic acid)
using colored class containers
using chain breakers such as alpha tocopherol
Using oxygen scavengers such as sodium metabisulfite and ascorbic acid
Ampicillin degrades much faster in water than in alcohol because
Water, being high dielectric constant solvent, converts the neutral ampicillin into a charged transition complex
Water, being a low dielectric constant solvent, converts the neutral ampicillin into a charged transition complex
none
Dissolution testing is conducted by manufacturers under what conditions?
Sink
Systemic
Supersaturation
Saturated
Generally, surface area does not remain constant throughout the dissolution process
true
false
what will be the effect on flux if the concentration gradient of a drug across a membrane would increase 2 fold?
flux would be doubled
Flux would remain unchanged
Flux would be increased by four times
Flux would be decreased by half
Hixson-Crowell Cube Root Law is capable of determining dissolution rate when
the shape of the dissolving particle is uniform and does not change during dissolution
The shape of the dissolving particle is random/irregular and does not change during dissolution
neither
