A prescription reads phenytoin 0.2 g orally twice daily. The medication label states that each capsule is 100 mg. The nurse prepares how many capsule(s) to administer 1 dose?

Choice A reason: Serotonin syndrome results from excessive serotonin, often from combining SSRIs and St. John’s Wort, which inhibits serotonin reuptake. Symptoms include dilated pupils (mydriasis) due to autonomic hyperactivity and loss of muscle coordination (ataxia) from neurological overstimulation, reflecting serotonin’s impact on motor control and sympathetic nervous system activation.

Choice B reason: Tinnitus and jerking movements are not primary features of serotonin syndrome. Tinnitus may occur in other conditions, like medication side effects, but is not typical here. Jerking movements could resemble myoclonus, but serotonin syndrome more consistently presents with autonomic symptoms (e.g., dilated pupils) and ataxia, making this choice less accurate.

Choice C reason: Pill-rolling movements and drooling are characteristic of Parkinson disease, not serotonin syndrome. These result from dopamine deficiency in the basal ganglia, unrelated to serotonin excess. Serotonin syndrome involves hyperactive neurological and autonomic symptoms, not parkinsonian features, making this choice incorrect for the condition described.

Choice D reason: Suicidal ideations are associated with depression or SSRI side effects but are not a hallmark of serotonin syndrome. This condition involves acute physiological symptoms like hyperthermia, tachycardia, and muscle rigidity due to serotonin toxicity, not primarily psychiatric manifestations, making this choice inappropriate.

Choice A reason: Congentin (benztropine), an anticholinergic used for parkinsonian symptoms, blocks acetylcholine, increasing sympathetic activity and causing tachycardia. This occurs as the parasympathetic inhibition of heart rate is reduced, leading to elevated heart rate, a common side effect in anticholinergic therapy, particularly in sensitive patients.

Choice B reason: Hallucinations are not a common side effect of Congentin. While anticholinergics can cause delirium or confusion, especially in older adults, hallucinations are more associated with dopaminergic agents or conditions like Lewy body dementia, not benztropine’s primary anticholinergic effects.

Choice C reason: Blurred vision is a frequent side effect of Congentin due to its anticholinergic properties, which inhibit parasympathetic control of the ciliary muscle, impairing accommodation. This leads to difficulty focusing, particularly at close range, and is a well-documented effect in patients taking anticholinergic medications.

Choice D reason: Confusion is a known side effect of Congentin, especially in older adults, due to its anticholinergic effects on the central nervous system. Blocking acetylcholine in the brain disrupts cognitive processing, leading to confusion, memory issues, or delirium, particularly in susceptible populations.

Choice E reason: Constipation is a common side effect of Congentin, as its anticholinergic action inhibits parasympathetic stimulation of gastrointestinal motility. This slows peristalsis, leading to reduced bowel movements and constipation, a frequent complaint in patients taking anticholinergic drugs like benztropine for parkinsonian symptoms.