Which of the following drugs is a reversible nonselective alfa beta antagonist?

Correct Answer: A

Rationale: Rationale: Labetalol is a reversible nonselective alpha-beta antagonist. It blocks both alpha and beta receptors. It is reversible due to its competitive binding, making it effective in managing hypertension. Phentolamine is an alpha blocker, not affecting beta receptors. Metoprolol and Propranolol are both beta blockers, targeting beta receptors only, making them selective and not reversible nonselective alpha-beta antagonists.

Correct Answer: C

Rationale: Carbamazepine is an antiepileptic drug that acts by blocking voltage-gated sodium channels, similar to Phenytoin. Both drugs inhibit sustained high-frequency repetitive firing of action potentials in neurons. Benzodiazepines (A) enhance inhibitory neurotransmission via GABA receptors, Valproate (B) inhibits GABA transaminase and increases GABA levels, and Ethosuximide (D) blocks T-type calcium channels, making them incorrect choices.

Correct Answer: B

Rationale: The correct answer is B: Clozapine. Clozapine is an atypical antipsychotic that can help counteract the behavioral complications of levodopa therapy, such as hallucinations and psychosis, without compromising the efficacy of levodopa. Tolkapone (A) is a COMT inhibitor used to prolong the effect of levodopa, not counteract behavioral complications. Carbidopa (C) is a dopa decarboxylase inhibitor that enhances levodopa's effectiveness but does not address behavioral complications. Pergolide (D) is a dopamine agonist used to treat Parkinson's disease symptoms, but it does not specifically target levodopa's behavioral complications.

Correct Answer: C

Rationale: Buprenorphine is a partial mu receptor agonist, meaning it activates the mu receptors but to a lesser extent compared to full agonists like morphine. Buprenorphine's unique pharmacological profile includes partial agonist activity at mu receptors, along with antagonist activity at kappa receptors. This combination results in a ceiling effect on respiratory depression and a lower risk of abuse potential compared to full agonists. Methadone is a full mu receptor agonist, morphine is a full mu receptor agonist, and sufentanyl is a potent full mu receptor agonist but is not a partial agonist like buprenorphine.

Correct Answer: B

Rationale: The correct answer is B: Clozapine. Clozapine is considered an atypical antipsychotic due to its unique mechanism of action targeting serotonin and dopamine receptors. It is commonly used for treatment-resistant schizophrenia. Haloperidol (A) is a typical antipsychotic. Thioridazine (C) and Thiothixene (D) are also typical antipsychotics. They primarily target dopamine receptors and are associated with more side effects compared to atypical antipsychotics like Clozapine.