Effects of morphine on CNS include all of the following EXCEPT:

Correct Answer: C

Rationale: Morphine, a mu-opioid receptor agonist, exerts profound CNS effects. Miosis (pinpoint pupils) results from parasympathetic stimulation via the Edinger-Westphal nucleus. Respiratory depression, a life-threatening effect, occurs due to reduced sensitivity of brainstem respiratory centers to CO2, a hallmark of opioid overdose. Depression of the cough reflex is mediated by medullary suppression, making morphine an antitussive. However, morphine lacks an anticonvulsant effect (choice C); it can lower the seizure threshold in overdose, potentially inducing convulsions, unlike drugs like benzodiazepines. This exception highlights morphine's CNS depressant profile, lacking the GABAergic enhancement needed for seizure control. Understanding these effects is vital for safe use, monitoring for overdose, and distinguishing morphine from anticonvulsant therapies.

Correct Answer: A

Rationale: Phenytoin treats status epilepticus (choice B), partial seizures (choice C), and digitalis-induced arrhythmias (choice D) by stabilizing sodium channels, reducing neuronal excitability or ectopic beats. Petit mal epilepsy (choice A), or absence seizures, responds better to ethosuximide or valproate, not phenytoin, which is ineffective against generalized absence seizures. This exception guides seizure-type-specific therapy.

Correct Answer: B

Rationale: Fluoxetine, an SSRI (choice A), treats depression, not epilepsy (choice B), by increasing serotonin. It can cause anxiety/insomnia (choice C) and sexual dysfunction (choice D) as side effects. Epilepsy treatment involves anticonvulsants, not SSRIs, making this the incorrect statement. This distinguishes psychiatric from neurological drug roles.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.