PLAB 1 Pharmacology & Prescribing 2

Question 1

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

Accepted Answer

Nephrotoxicity and ototoxicity

Answer

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.

Question 2

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

Accepted Answer

Calcium and vitamin D supplementation plus bisphosphonate

Answer

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.

Question 3

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

Accepted Answer

Beta-blocker

Answer

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.

Question 4

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

Accepted 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

Answer

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.

Question 5

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

Accepted Answer

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

Answer

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.

PLAB 1 Practice Test

PLAB 1 Practice Test

PLAB 1 Pharmacology & Prescribing 2