Core pharmacokinetic equations and biopharmaceutics concepts tested on the NAPLEX, as cloze cards with variables defined.
38 cards · cloze cards · AI-written, checked twice. Edit anything.
- The elimination half-life (t1/2) of a drug equals ____, where Vd is volume of distribution and CL is clearance.
- 0.693 x Vd / CL
- Volume of distribution (Vd) is calculated as ____, where C0 is the initial plasma concentration extrapolated to time zero.
- Dose / C0
- In first-order elimination kinetics, the rate of drug elimination is ____.
- directly proportional to the plasma drug concentration
- In zero-order elimination kinetics, a ____ of drug is eliminated per unit time, regardless of concentration.
- constant amount
- In first-order elimination kinetics, a constant ____ of drug is eliminated per unit time.
- fraction (percentage)
- How many half-lives are typically required to reach steady-state drug concentration?
- About 4 to 5 half-lives
- The loading dose formula is LD = ____, where Cp is the target plasma concentration and F is bioavailability.
- (Vd x Cp) / F
- The maintenance dose formula is MD = ____, where Css is the target steady-state concentration and tau is the dosing interval.
- (CL x Css x tau) / F
- Oral bioavailability (F) is calculated as ____ for equal doses.
- AUC(oral) / AUC(IV)
- What is the first-pass effect?
- Metabolism of an orally absorbed drug by the liver (or gut wall) before it reaches systemic circulation
- Hepatic extraction ratio (ER) equals ____, where Ca is drug concentration entering and Cv is drug concentration leaving the liver.
- (Ca - Cv) / Ca
- For a drug with a high hepatic extraction ratio, oral bioavailability is most limited by what factor?
- Hepatic blood flow
- Michaelis-Menten (saturable) kinetics is described by the equation dC/dt = ____.
- -Vmax x C / (Km + C)
- Name a classic drug that exhibits Michaelis-Menten (nonlinear) elimination kinetics at therapeutic doses.
- Phenytoin
- The therapeutic index (TI) is calculated as ____, comparing the toxic dose to the effective dose in 50% of a population.
- TD50 / ED50