MSRA Pharmacology and Prescribing Flashcards

A patient presents 4 hours after a suspected paracetamol overdose. What is the most important initial investigation?

Answer: Serum paracetamol level

The serum paracetamol level at 4 hours post-ingestion is plotted on the treatment nomogram to determine whether N-acetylcysteine (NAC) therapy is indicated.

A patient with end-stage renal failure requires analgesia for severe pain. Which opioid is most appropriate?

Answer: Fentanyl

Fentanyl is the preferred opioid in renal failure as it has no active metabolites; morphine and codeine accumulate toxic metabolites (morphine-6-glucuronide and norcodeine) that cause prolonged sedation and respiratory depression.

A patient on carbamazepine develops a skin rash. What is the most important immediate action?

Answer: Stop carbamazepine immediately

Carbamazepine can cause life-threatening cutaneous reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis; any rash warrants immediate drug discontinuation.

Which statement best describes first-order pharmacokinetics?

Answer: The rate of elimination is proportional to the drug concentration

In first-order kinetics, the rate of drug elimination is proportional to the plasma concentration, resulting in a constant half-life — the majority of drugs at therapeutic doses follow this pattern.

A patient started on amiodarone requires long-term monitoring. Which combination of side effects should be routinely screened for?

Answer: Thyroid dysfunction, hepatotoxicity, pulmonary toxicity, and corneal microdeposits

Amiodarone contains iodine, has an extremely long half-life (~40–55 days), and affects multiple organ systems: thyroid (hypo/hyperthyroidism), liver, lungs (fibrosis), and cornea (microdeposits), all requiring regular monitoring.

A patient with a mild penicillin allergy (urticarial rash, no anaphylaxis) requires treatment for community-acquired pneumonia. Which antibiotic is most appropriate?

Answer: A cephalosporin (e.g., cefuroxime)

In mild penicillin allergy (non-anaphylactic), cephalosporins can be used safely as the cross-reactivity rate is approximately 1–2%; a history of anaphylaxis would require a non-beta-lactam alternative.

A patient taking an SSRI for depression is prescribed tramadol for post-operative pain. What is the most serious potential drug interaction?

Answer: Serotonin syndrome

Tramadol inhibits serotonin and norepinephrine reuptake; combining it with an SSRI creates excess serotonergic activity, risking serotonin syndrome — characterised by hyperthermia, agitation, tremor, and hyperreflexia.