Problem 1: A drug in a liquid suspension form undergoes slow hydrolysis. The dependence of the drug concentration on time is as follows:

Time	Relative Drug concentration
Day 0	100%
Day 20	50%
Day 40	25%
Day 60	12.5%

Which statement about the apparent order of the hydrolysis reaction and the concentration dependence is correct?
Answers:

• zero order reaction, linear concentration decrease
• zero order reaction, exponential concentration decrease
• first order reaction, linear concentration decrease
• first order reaction, exponential concentration decrease
• second order reaction, quadratic concentration decrease

Problem 2: After the peak concentration of 270 μM is achieved for a drug in patient's plasma, the drug is slowly eliminated due to liver metabolism. 6 hours after the peak was reached, the plasma concentration dropped to 90 μM. How many hours must pass after the peak (NOT after the first measurement) so that the concentration drops to 10 μM? Assume first order reaction.
Answers:

• 48 hours
• 18 hours
• 2 hours
• 1 hour
• 12 hours
• 24 hours

Problem 3: Thalidomide undergoes spontaneous conversion from (+) form to (-) form and vice-versa, with the rate of conversion depending on the composition of the solution. For example, the half-life of (+)Thalidomide in human plasma is 11.5 minutes. Estimate the initial rate for the reaction of conversion of (+)Thalidomide into (-)Thalidomide in human plasma.
Answers:

• the initial concentration of (+)Thalidomide is needed to answer this question
• ln 2
• 1
• 0.087 min^-1
• 11.5 min
• 0.001 s^-1

Problem 4: Thalidomide undergoes spontaneous conversion from (+) form to (-) form and vice-versa, with the rate of conversion depending on the composition of the solution. For example, the half-life of (-)Thalidomide in human plasma is 8.33 minutes. Estimate the initial rate of conversion of (-)Thalidomide into (+)Thalidomide in a 500μM solution of enantiopure (-)Thalidomide in human plasma.
Answers:

• 8.33 μM
• ln 2 μM/s
• impossible to tell
• 500 s
• ln 2 / 500 M/s

Problem 5: Thalidomide undergoes spontaneous conversion from (+) form to (-) form and vice-versa, with the rate of conversion depending on the composition of the solution. For example, the half-life of (+)Thalidomide in human plasma is 11.5 minutes, and the half-life of (-)Thalidomide is 8.33 minutes. Find the equilibrium constant of the reaction, Th(+) <-> Th(-) (this constant is equal to the ratio [Th(-)]/[Th(+)] at equilibrium).
Answers:

• ln 2 / 8.33 min^-1
• ln 2 / 11.5 min^-1
• 0.725
• impossible to tell
• 42%
• 1

Problem 6: The rate constant for the reaction of binding of Indinavir to its target, HIV protease, is k_on = 1.53 x 10⁶ M^-1 s^-1 . What is the initial rate of formation of Indinavir-protease complexes in solution with [P] = 0.01 nM and [I] = 500 nM? The binding reaction has 1:1 stoichiometry and is first order in each of the reactants.
Answers:

• 2 x 10^-5 s^-1
• 5 nM²
• 765 nM
• 7.65 pM/s
• 1.53 x 10^-9 M/s

Problem 7: The rate constants, k, of a single molecule transformation (e.g. isomerization) are defined by the following factors:
Answers:

• concentration
• the energy barrier
• total amounts

Problem 8: 12 mg of a Fluoxetine was administered to a patient. The same amount of 1.2 mg are eliminated every hour as long as the drug is present. What is this elimination reaction order?
Answers:

• impossible to tell
• second
• first
• exponential decay
• zero