()ABCP Basic Science: Pharmacology Exam QUESTIONS AND ANSWERS

Differentiate pharmacokinetics from pharmacodynamics. - ANSWER Pharmacodynamics is the study of what the drug does to the body - Governs the concentration-effect part of the interaction Pharmacokinetics is what the body does to the drug - Governs the dosage-concentration part of the interaction What factors influence the extent of pharmacokinetic absorption? - ANSWER Strongly influenced by chemical solubility of the drug compound Route of administration Physiochemical properties of the drug Surface area available for absorption What happens with pharmacokinetic distribution? - ANSWER Occurs after absorption into blood stream Agents may be modified during distribution - Biotransformed or inactivated - Excreted without chemical change - Distributed to non-target areas - Bind to plasma proteins Define the first pass effect. - ANSWER Metabolism of a drug and its passage from the liver into the circulation Drug given orally may be extensively metabolized by the liver before reaching the systemic circulation (high first-pass effect) Same drug given IV bypasses the liver, preventing the first-pass effect from taking place, and more drug reaches the circulation Describe pharmacokinetic elimination. - ANSWER Excretion/clearance Terminates drug effect Most often via the kidney - Renal function impairment could prolong drug action or promote drug toxicity Can occur via other routes - Inhalation agents via the lungs - Skin via sweat - Bowels What are some effects of hypothermia on drug action? - ANSWER Hypothermia slows metabolism of drugs Clearance of drugs has been shown to be reduced - Propofol - Fentanyl - Morphine - Midazolam - Rocuronium - Vecuronium What are some effects of hemodilution on drug concentration? - ANSWER Hemodilution occurring at institution of CPB decreases circulating drug concentration Eventual plasma concentration of drug depends on: - Plasma protein binding - Original volume of distribution - Extent of equilibration between tissue and plasma at time of institution of CPB What are the effects of hemoconcentration on drug concentrations? - ANSWER Main determinant of passage through the hemofilter membrane is molecular weight Most drugs used on CPB have MW well below the pore size of 55-65kDa