Drug Distribution and Protein Binding — Flashcards

Flashcard 1: About _____% of phenytoin is bound to plasma proteins -mainly albumin

Answer: 90

Flashcard 2: When the rate of drug **administration** equals the rate of drug **elimination**, the drug has reached _____ concentration.

Answer: Steady-state concentration (Css)

Extra: Steady-state is achieved when the rate of drug administration (input) equals the rate of drug elimination (output). It typically takes 4–5 half-lives (t½) to reach steady-state. Formula for IV infusion: $Css = \frac{Rate\ of\ infusion}{Clearance}$

Flashcard 3: Loading dose is essential for chloroquine because of its property of _____

Answer: high Vd

Flashcard 4: Does morphine have a high plasma protein binding?_____

Answer: No

Flashcard 5: Time for peak plasma concentration (Tmax) of a drug indicates the rate of _____ from the administered site.

Answer: absorption

Flashcard 6: All barbiturates (thiopentone, thiamylal, methohexital) other than _____ are metabolized by liver

Answer: phenobarbitone

Flashcard 7: Thiopental is a barbiturate with a rapid onset and short duration of action due to its high _____ fraction and high lipid solubility.

Answer: unionized

Flashcard 8: The loading dose of a drug is governed primarily by its _____

Answer: Vd

Flashcard 9: What formula is used to calculate **loading dose**?

Answer: Loading Dose = $\frac{C_p \times V_d}{F}$

Extra: $C_p$ = target plasma concentration $V_d$ = volume of distribution $F$ = bioavailability

Flashcard 10: What is the formula for half-life (t1/2) in first-order elimination kinetics?

Answer: t1/2 = (0.693 × Vd) / CL

Extra: Where: - Vd = Volume of distribution - CL = Clearance Note: In first-order kinetics, the half-life is constant regardless of the plasma concentration.