B.Pharm. Bachelor of Pharmacy Biopharmaceutics & Pharmacokinetics 3

Question 1

In Michaelis-Menten kinetics, the Km value represents the substrate concentration at which the reaction velocity is:

Accepted Answer

Equal to half of Vmax

Answer

Km (Michaelis constant) is the drug concentration at which the rate of metabolic reaction is exactly half of the maximum velocity (Vmax); a lower Km indicates higher enzyme affinity for the substrate.

Question 2

A loading dose is administered to:

Accepted Answer

Rapidly achieve a therapeutic plasma concentration

Answer

A loading dose is a larger-than-maintenance initial dose given to rapidly achieve the target therapeutic plasma concentration, especially useful for drugs with long half-lives where accumulation to steady-state would otherwise take days.

Question 3

The primary factor limiting drug distribution across the blood-brain barrier (BBB) is the drug's:

Accepted Answer

Ionization state and lipophilicity

Answer

The BBB is composed of tight junction endothelial cells, so drugs must be un-ionized, lipophilic, and small to passively diffuse across; highly ionized or hydrophilic drugs are largely excluded.

Question 4

Renal clearance of a drug can be calculated using the formula:

Accepted Answer

Renal clearance = (Urine drug concentration × Urine flow rate) / Plasma drug concentration

Answer

Renal clearance is determined by multiplying urine drug concentration by urine flow rate (giving excretion rate) and dividing by plasma drug concentration, reflecting glomerular filtration, secretion, and reabsorption.

Question 5

The relationship between half-life (t½) and elimination rate constant (Ke) is expressed as:

Accepted Answer

t½ = 0.693 / Ke

Answer

For first-order elimination, t½ = 0.693 / Ke, where 0.693 is the natural log of 2 (ln 2); as Ke increases (faster elimination), the half-life decreases proportionally.

B.Pharm. Bachelor of Pharmacy Practice Test

B.Pharm. Bachelor of Pharmacy Practice Test

B.Pharm. Bachelor of Pharmacy Biopharmaceutics & Pharmacokinetics 3