Clinical Therapeutics & BNF Guidelines Flashcards

Which drug class is contraindicated in patients with asthma who require antihypertensive therapy?

Answer: Non-selective beta-blockers

Non-selective beta-blockers (e.g., propranolol) block beta-2 receptors in the bronchi, causing bronchoconstriction and worsening asthma. Even cardioselective beta-blockers should be used cautiously.

What is the mechanism of action of methotrexate in rheumatoid arthritis?

Answer: Inhibits dihydrofolate reductase, reducing DNA synthesis and inflammation

Methotrexate inhibits dihydrofolate reductase, reducing folate-dependent purine and pyrimidine synthesis, suppressing rapidly dividing immune cells involved in joint inflammation.

A patient taking clarithromycin is also prescribed simvastatin. What is the major concern?

Answer: Myopathy and rhabdomyolysis due to raised statin levels

Clarithromycin inhibits CYP3A4, significantly increasing simvastatin levels. This dramatically raises the risk of myopathy and rhabdomyolysis. Simvastatin should be suspended during clarithromycin treatment.

Which antibiotic class acts by inhibiting cell wall synthesis by binding penicillin-binding proteins?

Answer: Beta-lactams (penicillins, cephalosporins)

Beta-lactam antibiotics (penicillins, cephalosporins, carbapenems) inhibit transpeptidase enzymes (penicillin-binding proteins) that cross-link peptidoglycan in bacterial cell walls.

What is the first-line treatment for Clostridium difficile infection according to UK guidelines?

Answer: Oral vancomycin or fidaxomicin

UK guidelines (PHE/NICE) recommend oral vancomycin or fidaxomicin as first-line treatment for C. difficile infection. Oral metronidazole is no longer first-line.

A patient requires anticoagulation but has heparin-induced thrombocytopenia (HIT). Which anticoagulant is appropriate?

Answer: Argatroban or fondaparinux

In HIT, all heparin products (including LMWH) are contraindicated due to cross-reactivity with anti-platelet factor 4 antibodies. Argatroban (direct thrombin inhibitor) or fondaparinux are used instead.