Clinical Pharmacology Flashcards

What is the clinical significance of first-pass metabolism for oral drug administration?

Answer: It reduces the bioavailability of oral drugs by metabolising them in the gut wall and liver before reaching systemic circulation

First-pass metabolism by gut wall enzymes and hepatic CYP450 enzymes can substantially reduce the amount of oral drug reaching systemic circulation, requiring higher oral doses compared to IV routes.

A patient with renal impairment (GFR 20 mL/min) is prescribed gentamicin. Why is dose adjustment needed?

Answer: Gentamicin is renally excreted; reduced GFR causes drug accumulation leading to nephrotoxicity and ototoxicity

Gentamicin is almost entirely eliminated by glomerular filtration; reduced GFR leads to drug accumulation, increasing plasma levels and the risk of nephrotoxicity and irreversible ototoxicity.

Which drug class is used as the antidote for benzodiazepine overdose?

Answer: Flumazenil (GABA-A receptor antagonist)

Flumazenil competitively antagonises benzodiazepine binding at the GABA-A receptor, rapidly reversing sedation, respiratory depression, and other CNS effects of benzodiazepine overdose.

Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins?

Answer: Beta-lactams (penicillins, cephalosporins, carbapenems)

Beta-lactam antibiotics bind to penicillin-binding proteins (PBPs) on the bacterial surface, blocking transpeptidation and cross-linking of peptidoglycan chains, leading to cell wall lysis.

What is the primary mechanism by which statins lower LDL cholesterol?

Answer: Competitive inhibition of HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptors

Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis, causing compensatory upregulation of LDL receptors that clear LDL from the blood.

Which clinical parameter is monitored to assess lithium toxicity in a patient being treated for bipolar disorder?

Answer: Serum lithium levels, renal function, and thyroid function

Lithium has a narrow therapeutic index; serum levels must be monitored regularly along with renal function (lithium is renally excreted) and thyroid function (lithium causes hypothyroidism).