Pharmacology & Prescribing Flashcards

A 65-year-old man is prescribed gentamicin for a Gram-negative infection. Which of the following side effects must be specifically monitored?

Answer: Nephrotoxicity and ototoxicity

Aminoglycosides (gentamicin, amikacin) cause nephrotoxicity (tubular damage) and ototoxicity (vestibular and cochlear damage), particularly with prolonged use or high trough levels. Regular monitoring of renal function and gentamicin levels (trough and peak, or once-daily AUC monitoring) is essential.

A patient on long-term oral steroids (prednisolone) requires co-prescription of which of the following to prevent a common serious side effect?

Answer: Calcium and vitamin D supplementation plus bisphosphonate

Long-term corticosteroids cause significant bone loss (osteoporosis) through multiple mechanisms. NICE guidelines (CG146) recommend calcium and vitamin D for all patients on steroids, and bisphosphonates (e.g., alendronate) for patients at moderate/high risk of fracture. This is one of the most important co-prescriptions in clinical practice.

A patient with asthma develops worsening bronchoconstriction after being prescribed a new medication for hypertension. Which class of drug is most likely responsible?

Answer: Beta-blocker

Beta-blockers (even cardioselective ones like atenolol) are contraindicated in asthma because they can cause bronchospasm by blocking beta-2 receptors in bronchial smooth muscle. Non-selective beta-blockers (propranolol) carry greater risk. This is a key prescribing safety rule.

A 28-year-old woman of childbearing age with epilepsy is prescribed valproate. What is the most important counselling point?

Answer: Valproate is highly teratogenic (risk of neural tube defects, neurodevelopmental effects) and must not be used in women who may become pregnant without specialist review and the Pregnancy Prevention Programme

Sodium valproate has high teratogenic risk — 10% risk of congenital malformations (especially neural tube defects) and 30–40% risk of neurodevelopmental problems. UK MHRA requires implementation of the Pregnancy Prevention Programme (contraception, annual review, patient card) for all women of childbearing potential on valproate.

A patient is prescribed trimethoprim for a UTI. They are also on methotrexate for rheumatoid arthritis. What is the key interaction?

Answer: Both are folate antagonists — co-administration markedly increases the risk of methotrexate toxicity (pancytopenia)

Both trimethoprim and methotrexate are folate antagonists. Concurrent use markedly increases the risk of methotrexate toxicity — particularly haematological toxicity (bone marrow suppression, pancytopenia). This combination should be avoided; an alternative antibiotic should be prescribed.

A 45-year-old man with a history of peptic ulcer disease requires an NSAID for acute gout. What should be co-prescribed to reduce the risk of GI complications?

Answer: A proton pump inhibitor (PPI)

NSAIDs inhibit COX-1 and COX-2, reducing gastric mucosal protection and increasing the risk of peptic ulcers and GI bleeding. PPI co-prescription is recommended by NICE for patients on NSAIDs who have risk factors (previous ulcer, age >65, oral steroids, anticoagulants). A PPI reduces GI complications significantly.