You are a resident in a hospital in a very poor part of the world. Their drug selection is limited. A patient presents with acute cardiac failure, for which your preferred drug is dobutamine, given intravenously. However, there is none available. Which of the following other drugs, or combination of drugs, would be a suitable alternative?

Correct Answer: D

Rationale: The correct answer is D: Norepinephrine plus phentolamine. Norepinephrine is a potent vasopressor that can increase blood pressure and cardiac output in acute cardiac failure. Phentolamine is an alpha-blocker that can help counteract the vasoconstrictive effects of norepinephrine. Rationale: 1. Norepinephrine: Increases blood pressure and cardiac output, improving perfusion to vital organs in acute cardiac failure. 2. Phentolamine: Counteracts the vasoconstrictive effects of norepinephrine, preventing excessive vasoconstriction. Summary: A: Dopamine at a very high dose may not be as effective as norepinephrine in acute cardiac failure. B: Ephedrine is a less potent vasopressor compared to norepinephrine. C: Ephedrine plus propranolol combination may lead to conflicting effects on blood pressure and heart rate

Correct Answer: C

Rationale: The correct answer is C: Amphetamine. Amphetamine is not a catecholamine because it is a synthetic drug, not naturally produced by the body like adrenaline (A), noradrenaline (B), and isoprenaline (D). Catecholamines are a class of neurotransmitters that include dopamine, adrenaline, and noradrenaline, all of which have a catechol group in their chemical structure. Amphetamine, on the other hand, is a substituted phenethylamine with no catechol group. This distinction makes amphetamine the only non-catecholamine among the given options.

Correct Answer: D

Rationale: The correct answer is D: Stimulate muscarinic receptors. Parasympathomimetic drugs mimic the actions of the parasympathetic nervous system, which primarily uses acetylcholine on muscarinic receptors to produce its effects. By stimulating muscarinic receptors, these drugs enhance parasympathetic activity. A, B, and C are incorrect: A: Inhibiting muscarinic receptors would have the opposite effect of parasympathomimetic drugs. B: Inhibiting the release of acetylcholine would also reduce parasympathetic activity. C: Inhibiting adrenergic receptors pertains to the sympathetic nervous system, not the parasympathetic system targeted by parasympathomimetic drugs.

Correct Answer: B

Rationale: The correct answer is B: Trimetaphan. Nicotinic receptors are blocked by non-depolarizing neuromuscular blockers like Trimetaphan. Propranolol (A) is a beta-blocker, Prazosin (C) is an alpha-1 blocker, and Pilocarpine (D) is a muscarinic agonist, none of which block nicotinic receptors. Therefore, Trimetaphan (B) is the only choice that directly blocks nicotinic receptors.

Correct Answer: D

Rationale: Selective beta2 stimulants typically cause skeletal muscle tremors due to their action on beta2 receptors in skeletal muscles. They can also lead to tolerance with prolonged use, requiring higher doses for the same effect. Additionally, they can cause tachycardia by stimulating beta2 receptors in the heart. Therefore, all of the above choices (A, B, and C) are correct.