Biopharmaceutics & Pharmacokinetics Flashcards
7 cards from real B.Pharm. Bachelor of Pharmacy practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Biopharmaceutics & Pharmacokinetics flashcards as text
In Michaelis-Menten kinetics, the Km value represents the substrate concentration at which the reaction velocity is:
Answer: Equal to half of Vmax
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.
A loading dose is administered to:
Answer: Rapidly achieve a therapeutic plasma concentration
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.
The primary factor limiting drug distribution across the blood-brain barrier (BBB) is the drug's:
Answer: Ionization state and lipophilicity
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.
Renal clearance of a drug can be calculated using the formula:
Answer: Renal clearance = (Urine drug concentration × Urine flow rate) / Plasma drug concentration
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.
The relationship between half-life (t½) and elimination rate constant (Ke) is expressed as:
Answer: t½ = 0.693 / Ke
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.
According to FDA bioequivalence criteria, a generic drug is considered bioequivalent to the reference listed drug when its 90% confidence interval for AUC and Cmax ratios falls within:
Answer: 80–125% of the reference product
The FDA requires that the 90% confidence interval for the ratio of AUC and Cmax of the test to reference product falls within 80–125%, ensuring therapeutic equivalence between generic and brand-name drugs.
According to the Henderson-Hasselbalch equation, a weakly acidic drug with pKa of 4.0 will be predominantly absorbed in the stomach (pH 1.5) because:
Answer: The drug exists mostly in the un-ionized lipid-soluble form at gastric pH below its pKa
For weakly acidic drugs, when gastric pH (1.5) is much lower than the drug's pKa (4.0), the drug exists predominantly in the un-ionized, lipophilic form, which readily crosses lipid membranes and is absorbed.