Pharmacology Flashcards

A patient with myasthenia gravis is given an aminoglycoside antibiotic and develops respiratory failure. What is the mechanism of this drug interaction?

Answer: Aminoglycosides block neuromuscular junction transmission

Aminoglycosides have neuromuscular blocking properties — they inhibit presynaptic acetylcholine release and block postsynaptic receptors. In myasthenia gravis patients (who already have reduced acetylcholine receptors due to autoantibodies), this can precipitate a myasthenic crisis with respiratory failure.

A patient on phenytoin is noted to have gingival hyperplasia, hirsutism, and a serum albumin of 25 g/L. How does hypoalbuminaemia affect phenytoin dosing?

Answer: Increased free drug levels — may appear therapeutic but cause toxicity

Phenytoin is >90% protein-bound. In hypoalbuminaemia, more free (unbound) phenytoin is available, increasing pharmacological effect and toxicity risk even when total phenytoin levels appear therapeutic. Adjusted phenytoin levels or free phenytoin levels should be measured.

Which drug is the first-line treatment for status epilepticus?

Answer: Diazepam or lorazepam IV

IV benzodiazepines (lorazepam preferred, diazepam alternative) are first-line for acute status epilepticus. Lorazepam (0.1 mg/kg IV) has a longer duration of action in the CNS than diazepam. If benzodiazepines fail, second-line agents include phenytoin/fosphenytoin, valproate, or levetiracetam.

A patient taking a monoamine oxidase inhibitor (MAOI) eats a meal containing aged cheese and develops a severe hypertensive crisis. What substance in the cheese caused this reaction?

Answer: Tyramine

Tyramine is found in aged cheeses, cured meats, and fermented foods. Normally, tyramine is metabolised by MAO in the gut wall and liver. When MAO is inhibited, tyramine is absorbed intact and causes massive noradrenaline release from sympathetic nerve endings, resulting in a hypertensive crisis.

Which medication used in type 2 diabetes is associated with weight loss and reduced cardiovascular events?

Answer: Liraglutide (GLP-1 receptor agonist)

GLP-1 receptor agonists (liraglutide, semaglutide) promote weight loss through central appetite suppression, slow gastric emptying, and improve glycaemic control. The LEADER trial demonstrated cardiovascular mortality benefit with liraglutide in type 2 diabetes patients with CVD.

A patient is prescribed gentamicin for a serious gram-negative infection. Which two adverse effects require monitoring?

Answer: Nephrotoxicity and ototoxicity

Aminoglycosides (gentamicin, tobramycin, amikacin) require monitoring for nephrotoxicity (elevated creatinine, reduced GFR) and ototoxicity (vestibular and cochlear damage causing dizziness and hearing loss). Trough and/or peak levels guide dosing to minimise toxicity.