Drug resistance is a term used to describe the loss of effectiveness of antimicrobial or antitumour drugs. This consideration is:

Correct Answer: A

Rationale: Drug resistance refers to the ability of microbes or cancer cells to withstand the effects of drugs designed to kill or inhibit their growth. This loss of effectiveness is a significant concern in healthcare. Therefore, the statement that drug resistance is a term used to describe the loss of effectiveness of antimicrobial or antitumour drugs is TRUE. Summary of other choices: - B: FALSE - Incorrect, as drug resistance is a real phenomenon affecting the efficacy of drugs. - C: None of the above - Incorrect, as option A is correct. - D: All of the above - Incorrect, as not all options are valid; only option A is correct.

Correct Answer: B

Rationale: The correct answer is B: Hexamethonium. Ganglion-blocking drugs act by blocking nicotinic receptors in autonomic ganglia, leading to decreased sympathetic and parasympathetic responses. Hexamethonium is a ganglion-blocking drug that specifically acts on ganglionic nicotinic receptors. - A: Homatropine is a muscarinic antagonist used to dilate the pupil. - C: Rapacuronium is a non-depolarizing neuromuscular blocking agent. - D: Edrophonium is an acetylcholinesterase inhibitor used for the diagnosis of myasthenia gravis.

Correct Answer: D

Rationale: The correct answer is D: Succinylcholine. Succinylcholine can cause cardiac arrhythmias by inducing hyperkalemia, especially in patients with certain conditions like burns, denervation injuries, or spinal cord injuries. This hyperkalemia can lead to dangerous arrhythmias such as ventricular tachycardia or fibrillation. Vecuronium (A), Tubocurarine (B), and Rapacuronium (C) are not known to cause cardiac arrhythmias as they do not have the same mechanism of action as Succinylcholine.

Correct Answer: B

Rationale: The correct answer is B: Bronchodilation. Ephedrine is a sympathomimetic amine that acts on alpha and beta adrenergic receptors. It primarily stimulates beta-2 adrenergic receptors in the lungs, leading to bronchodilation. This action helps in the treatment of asthma and other respiratory conditions. Miosis (choice A) is constriction of the pupil, which is not a known effect of ephedrine. Hypotension (choice C) is low blood pressure, but ephedrine is more likely to cause hypertension due to its vasoconstrictive effects. Bradycardia (choice D) is a slow heart rate, but ephedrine usually causes tachycardia due to its stimulatory effects on the heart.

Correct Answer: C

Rationale: The correct answer is C: Nadolol. Nadolol is a non-selective beta blocker with a long half-life, leading to an extended duration of action. It is typically dosed once daily, making it convenient for patients. Metoprolol (A) and Propranolol (B) have shorter durations of action compared to Nadolol. Pindolol (D) is a partial beta agonist and does not exhibit a long duration of action like Nadolol.