Which of the following drugs causes bronchodilation without significant cardiac stimulation?

Correct Answer: B

Rationale: The correct answer is B: Terbutaline. Terbutaline is a selective beta-2 adrenergic agonist that causes bronchodilation by acting on beta-2 receptors in the lungs without significant cardiac stimulation. Isoprenaline (A) is a non-selective beta agonist that can cause significant cardiac stimulation. Xylometazoline (C) is a nasal decongestant that acts on alpha-adrenergic receptors and does not cause bronchodilation. Methoxamine (D) is an alpha-1 adrenergic agonist that can actually cause bronchoconstriction and does not cause bronchodilation.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: Hepatic microsomal drug-metabolizing enzyme induction increases the metabolism of drugs like barbiturates. This leads to decreased drug levels, resulting in tolerance - requiring higher doses for the same effect. Choices B, C, and D are incorrect because cumulative effects refer to increased drug levels due to impaired metabolism, physical dependence is related to behavioral aspects, and hangover effects are due to drug toxicity or residual effects, not enzyme induction.

Correct Answer: A

Rationale: The correct answer is A. Carbamazepine is an antiepileptic drug known to cause dose-related adverse effects such as diplopia (double vision), ataxia (lack of coordination), and nausea. Diplopia and ataxia are common neurological side effects, while nausea is a gastrointestinal side effect. This is due to the drug's mechanism of action on sodium channels in the nervous system. Choices B, C, and D are incorrect. Gingival hyperplasia and hirsutism are not common adverse effects of carbamazepine. Sedation and dependence are more associated with benzodiazepines, and hemeralopia and myasthenic syndrome are not typically linked to carbamazepine use.

Correct Answer: D

Rationale: The correct answer is D because all three drugs (Reserpine, Haloperidol, Chlorpromazine) antagonize the effects of levodopa by different mechanisms, leading to a junctional blockade of dopamine action. Reserpine depletes dopamine stores, Haloperidol blocks dopamine receptors, and Chlorpromazine inhibits dopamine release. Therefore, all of these drugs can reduce the effectiveness of levodopa in treating Parkinson's disease by interfering with dopamine function. Choices A, B, and C are incorrect because each of them individually, not collectively, antagonizes the effects of levodopa and leads to a junctional blockade of dopamine action.

Correct Answer: C

Rationale: Rationale: 1. Nalbuphine is a strong kappa receptor agonist: It primarily activates kappa receptors, providing analgesia. 2. Nalbuphine is a mu receptor antagonist: It blocks mu receptors, reducing the risk of mu receptor-associated side effects. 3. Naltrexone (A) is a mu receptor antagonist but not a kappa agonist. 4. Methadone (B) is a mu receptor agonist and NMDA receptor antagonist. 5. Buprenorphine (D) is a partial mu receptor agonist and kappa receptor agonist, not a mu antagonist like nalbuphine.