Schizophrenia Q 47
A client receiving fluphenazine decanoate (Prolixin Decanoate) therapy develops pseudoparkinsonism. The physician is likely to prescribe which drug to control this extrapyramidal effect?
A. diphenhydramine (Benadryl)
B. phenytoin (Dilantin)
C. benztropine (Cogentin)
D. amantadine (Symmetrel)
Correct Answer: D. amantadine (Symmetrel)
An antiparkinsonian agent, such as amantadine, may be used to control pseudoparkinsonism. Amantadine is now used mostly for Parkinson’s disease. Clinical trials have shown that amantadine decreases symptoms of bradykinesia, rigidity, and tremor. There is a combined synergistic effect with added levodopa, which is converted to dopamine by striatal enzymes in the CNS. There can be a transient benefit to the drug, so short-term therapy for patients with mild disease is best.
Option A: Diphenhydramine may be used to control other extrapyramidal effects. Diphenhydramine, which is available as an over-the-counter medication, is a first-generation antihistamine that is used in a variety of conditions to treat and prevent dystonias, insomnia, pruritus, urticaria, vertigo, and motion sickness. The H1 receptor is similar to muscarinic receptors. Therefore, diphenhydramine also acts as an antimuscarinic; it is a competitive antagonist of muscarinic acetylcholine receptor, resulting in its use as an antiparkinson medication.
Option B: Phenytoin is used to treat seizure activity. The FDA approved phenytoin in 1939 for the treatment of epilepsy. Despite its narrow therapeutic index, the drug has seen robust use in the treatment of generalized tonic-clonic seizures, complex partial seizures, status epilepticus, trigeminal neuralgia, and behavior disorders. Phenytoin is a hydantoin derivative, a first-generation anticonvulsant drug that is effective in the treatment of generalized tonic-clonic seizures, complex partial seizures, and status epilepticus without significantly impairing neurological function.
Option C: Benztropine belongs to the synthetic class of muscarinic receptor antagonists (anticholinergic drug). It is also useful for drug-induced extrapyramidal symptoms and the prevention of dystonic reactions and acute treatment of dystonic reactions. It also induces less CNS stimulation effect compared to that of trihexyphenidyl, making it a preferable drug of choice for geriatric patients. Moreover, benztropine is FDA approved as adjunctive therapy of all forms of parkinsonism.