Pharmacodynamics and Pharmacokinetics EC Flashcards
What is second order kinetics?
Rate independent of substrate concentration
What is first order kinetics?
Rate proportional to substrate concentration
Does a competitive inhibitor change Km or Vmax? How?
Competitive inhibitors increase Km but have no effect on Vmax.
Decrease potency
Does a noncompetitive (irreversible) inhibitor change Km or Vmax? How
Noncompetitive inhibitors decrease Vmax but have no effect on Km
Decrease efficacy
What is the formula for calculating volume of distrobution?
= drug in body/plasma drug concentration
What does a high/medium/low volume of distribution mean?
High=all tissues=small lipophilic
Medium=ECF=Small hydrophilic molecules
Low=Blood=Large/charged molecules
What is the equation for half life?
= (0.7 * Vd) / Clearance (CL)
What is the equation for loading dose?
= Css * Vd / (F)
F=bioavailability, usually= 1 in questions
What is the equation for maintenance dose?
= Css * CL / (F)
What is first order elimination?
Flow dependent elimination
PROPORTIONAL TO CONCENTRATION (ie set fraction)
What is zero order elimination?
Capacity dependent elimination
CONSTANT AMOUNT ELIMINATED
“PEA” - phenytoin, ethanol, aspirin
What is phase I metabolism?
Reduction, oxidation, or hydrolysis via CYP450
geriatrics lose phase I first
What is phase II metabolism?
Conjugation (glucouronidation, acetylation, sulfation).
Renally excreted
What is therapeutic index?
Lethal dose / Effective dose
Large TI means drug is safe
What are some examples of drugs with low therapeutic indexes?
Digoxin, Lithium, theophylline, & warfarin
