Pharmacology Fundamentals Flashcards

Which property of inhaled anaesthetic agents is best predicted by the oil-gas partition coefficient?

Answer: Minimum alveolar concentration (MAC)

MAC correlates inversely with the oil-gas partition coefficient (lipid solubility), consistent with the Meyer-Overton hypothesis of anaesthetic potency.

A patient on clopidogrel requires emergency CABG. The most appropriate management regarding antiplatelet reversal is:

Answer: Delay surgery 5–7 days to allow new platelet generation if clinically safe

Clopidogrel irreversibly inhibits P2Y12 receptors on platelets; since platelet lifespan is ~7–10 days, waiting 5–7 days allows sufficient new platelet generation to reduce bleeding risk.

The analgesic effect of paracetamol (acetaminophen) is thought to be mediated primarily through:

Answer: Inhibition of COX-3 and activation of the descending serotonergic pathway

Paracetamol inhibits a COX variant in the CNS and activates descending serotonergic/cannabinoid pain-modulating pathways, explaining its central analgesic mechanism.

In a patient with acute kidney injury, which benzodiazepine has the most predictable pharmacokinetics due to direct glucuronidation without active metabolites?

Answer: Lorazepam

Lorazepam undergoes direct glucuronidation to inactive metabolites without hepatic CYP450 oxidation, making it more predictable in renal or hepatic impairment.

A septic patient on noradrenaline shows no haemodynamic response despite dose escalation to 1 mcg/kg/min. Adding vasopressin is most useful because:

Answer: Sepsis depletes endogenous vasopressin and V1 receptors remain functional on vascular smooth muscle

Vasopressin levels fall in prolonged septic shock while V1 vasopressin receptors on smooth muscle remain responsive, providing a noradrenaline-sparing pressor effect.

Which statement accurately describes the pharmacology of tranexamic acid (TXA) in trauma?

Answer: TXA is a lysine analogue that competitively inhibits plasminogen binding to fibrin, reducing fibrinolysis

Tranexamic acid mimics lysine and competitively occupies lysine-binding sites on plasminogen, preventing its activation to plasmin and thereby reducing fibrinolysis.

Which of the following is the most appropriate analgesic choice for a mechanically ventilated ICU patient with anuria and rhabdomyolysis?

Answer: Fentanyl infusion, as it does not accumulate active metabolites in renal failure

Fentanyl is preferred in renal failure as it has no clinically significant active metabolites; morphine's M6G metabolite accumulates in renal impairment causing prolonged sedation and respiratory depression.