DHA Pharmacist Clinical Pharmacology 2 — Questions and Answers
Question 1: What is the clinical significance of first-pass metabolism for oral drug administration?
- It reduces the bioavailability of oral drugs by metabolising them in the gut wall and liver before reaching systemic circulation (Correct answer)
- It increases the drug's potency
- It only affects intravenous drugs
- It has no clinical relevance in modern pharmacy
Correct 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.
Question 2: A patient with renal impairment (GFR 20 mL/min) is prescribed gentamicin. Why is dose adjustment needed?
- Gentamicin is renally excreted; reduced GFR causes drug accumulation leading to nephrotoxicity and ototoxicity (Correct answer)
- The drug becomes more effective in renal impairment
- Renal impairment enhances absorption of gentamicin
- No adjustment is needed for renally excreted drugs
Correct 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.
Question 3: Which drug class is used as the antidote for benzodiazepine overdose?
- Flumazenil (GABA-A receptor antagonist) (Correct answer)
- Naloxone (opioid antagonist)
- N-acetylcysteine (paracetamol antidote)
- Protamine sulphate (heparin antidote)
Correct 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.
Question 4: Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins?
- Beta-lactams (penicillins, cephalosporins, carbapenems) (Correct answer)
- Fluoroquinolones
- Macrolides
- Aminoglycosides
Correct 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.
Question 5: What is the primary mechanism by which statins lower LDL cholesterol?
- Competitive inhibition of HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptors (Correct answer)
- Increasing bile acid excretion
- Activating lipoprotein lipase
- Blocking cholesterol absorption in the gut
Correct 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.
Question 6: Which clinical parameter is monitored to assess lithium toxicity in a patient being treated for bipolar disorder?
- Serum lithium levels, renal function, and thyroid function (Correct answer)
- Liver enzymes only
- Platelet count only
- Blood glucose levels
Correct 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).
DHA Pharmacist Clinical Pharmacology 2
What is the clinical significance of first-pass metabolism for oral drug administration?