Indicate the irreversible alfa receptor antagonist:

Correct Answer: D

Rationale: Step-by-step rationale for why Phenoxybenzamine (choice D) is the correct answer: 1. Phenoxybenzamine is an irreversible alpha receptor antagonist, blocking alpha-1 and alpha-2 receptors. 2. It forms covalent bonds with the receptors, leading to long-lasting and irreversible blockade. 3. This irreversible binding distinguishes Phenoxybenzamine from reversible alpha blockers like Prazosin (choice C). 4. Tolazoline (choice A) is a nonselective alpha blocker, and Labetalol (choice B) is a mixed alpha and beta blocker, but neither are irreversible. Summary: Phenoxybenzamine is the correct choice as it irreversibly blocks alpha receptors, unlike the other options which are either nonselective or reversible blockers.

Correct Answer: B

Rationale: Phenytoin is primarily used for treating Grand mal epilepsy, also known as tonic-clonic seizures. This is because Phenytoin is effective in controlling the spread of seizure activity in the brain. Petit mal epilepsy is better treated with other medications like Ethosuximide, and myoclonic seizures are typically managed with different drugs like valproic acid. Therefore, the correct answer is B as Phenytoin is specifically indicated for treating Grand mal epilepsy.

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. Carbidopa cannot cross the blood-brain barrier due to its large molecular size. 2. Carbidopa inhibits peripheral DOPA decarboxylase, preventing levodopa breakdown outside the brain. 3. By reducing peripheral levodopa conversion, carbidopa increases levodopa availability to cross the blood-brain barrier. 4. This results in more levodopa reaching the brain for conversion to dopamine, enhancing its central effects. Summary: - Choice A is true as carbidopa indeed prevents peripheral levodopa breakdown, enhancing its central effects. - Choice B is incorrect because carbidopa does not act within the brain itself. - Choice C is incorrect as there is a correct answer. - Choice D is incorrect as not all statements are true.

Correct Answer: D

Rationale: The correct answer is D: Abstinence syndrome. These symptoms are characteristic of opioid withdrawal, which occurs when a person dependent on opioids suddenly stops or reduces their use. Rhinorrhea, lacrimation, chills, gooseflesh, and other symptoms listed are commonly seen during opioid withdrawal due to the body's reaction to the absence of the drug. Tolerance (A) refers to a decreased response to a drug over time, not withdrawal symptoms. Opioid overdosage (B) would present with different symptoms such as respiratory depression. Drug interactions (C) may lead to various side effects but wouldn't produce the specific withdrawal symptoms listed.

Correct Answer: B

Rationale: The correct answer is B: The pituitary. Dopamine inhibits prolactin release from the pituitary gland. Blockade of dopamine receptors in the pituitary leads to increased prolactin levels, causing hyperprolactinemia. Choices A, C, and D are incorrect as they are not directly involved in regulating prolactin release. A is related to nausea and vomiting control, C is associated with motor functions, and D is involved in reward and motivation pathways.