Pharmacology questions that explain themselves.

Answer: Reduces hepatic glucose output without causing hypos

Metformin cuts hepatic glucose production and improves insulin sensitivity. Because it never pushes insulin above what the glucose load justifies, it does not cause hypoglycaemia on its own, and it avoids the weight gain that insulin-releasing drugs bring.

Answer: Is protein-bound and CYP-metabolised, with a narrow index

Three properties stack. High protein binding means displacement matters, CYP2C9 metabolism means induction and inhibition matter, and a narrow index means neither has to shift much before the INR leaves the target range.

Answer: Amiodarone, macrolides and several antipsychotics

These drugs delay cardiac repolarisation, usually by blocking the rapid potassium current, which lengthens the QT interval and creates the window in which torsades can start. The risk compounds when two such drugs are combined or when potassium and magnesium are low.

Answer: A competitive antagonist at the benzodiazepine site

Flumazenil occupies the benzodiazepine binding site without activating it, displacing the drug by competition. It is used cautiously, because abruptly removing benzodiazepine activity can precipitate seizures in a dependent patient.

Answer: It is a prodrug needing CYP2D6 to form morphine

Codeine has little activity at the mu receptor and depends on conversion to morphine. CYP2D6 activity is genetically variable, so poor metabolisers make too little morphine to feel anything, while ultra-rapid metabolisers can reach toxic levels from a normal dose.

Answer: Tremor and palpitations warning of a low glucose

The early warnings of a falling glucose are sympathetic, so beta blockade removes the signal while leaving the danger. Sweating is cholinergic and usually persists, which makes it the one symptom that may still break through.

Answer: It blocks β₂ receptors in bronchial smooth muscle

Propranolol is non-selective, so the β₂ receptors that keep airways open are blocked alongside the cardiac β₁ receptors that were the target. Cardioselective agents such as bisoprolol exist precisely to narrow that effect.

Answer: Prevent the breakdown of bradykinin in the airway

ACE also degrades bradykinin, so inhibiting the enzyme lets bradykinin build up in the airways. ARBs act at the receptor instead, leave bradykinin breakdown untouched, and therefore avoid the cough.

Answer: Acts immediately and is reversed using protamine

Heparin potentiates antithrombin directly, so it works at once, is tracked by aPTT and is reversed by protamine. Warfarin has to wait for existing clotting factors to be cleared, which is why it is slow, INR-monitored and vitamin K reversible.

Answer: Report unexplained muscle pain without delay

Myopathy matters because it can progress to rhabdomyolysis, and the risk climbs with statin plasma concentration. Most statins are CYP3A4 substrates, so an inhibitor raises the level and the risk along with it.