The nurse must administer a medication to reverse or prevent Parkinson-type symptoms in a client receiving an antipsychotic. The medication the client will likely receive is:
A. benztropine (Cogentin)
B. diphenhydramine (Benadryl)
C. propranolol (Inderal)
D. haloperidol (Haldol)
Correct Answer: A. benztropine (Cogentin)
Benztropine, trihexyphenidyl, or amantadine are prescribed for a client with Parkinson-type symptoms. It is also useful for drug-induced extrapyramidal symptoms and the prevention of dystonic reactions and acute treatment of dystonic reactions. Furthermore, benztropine has further off-label use as it can treat chronic sialorrhea occurring in developmentally-disabled patients. Benztropine antagonizes acetylcholine and histamine receptors. In the CNS and smooth muscles, benztropine exerts its action through competing with acetylcholine at muscarinic receptors. Consequently, it reduces central cholinergic effects by blocking muscarinic receptors that appear to improve the symptoms of Parkinson disease. Thus, benztropine blocks the cholinergic muscarinic receptor in the central nervous system. Therefore, it reduces the cholinergic effects significantly during Parkinson disease which becomes more pronounced in the nigrostriatal tract because of reduced dopamine concentrations.
Option B: Diphenhydramine provides rapid relief for dystonia. 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. It also possesses local anesthetic properties for those patients who have allergies to other, more commonly used local anesthetics; however, this is an off-label use of the medication.
Option C: Propranolol relieves akathisia. Beta-blockers such as propranolol and benzodiazepines have historically been used for the treatment of akathisia although the amount of high-quality data supporting their use is limited. When using beta-blockers, clinicians should be aware of the risk of bradycardia and hypotension.
Option D: Haloperidol can cause Parkinson-type symptoms. Toxicities are the exaggerated symptoms of known pharmacologic effects and known adverse reactions. The most prominent toxicities of haloperidol are 1) severe extrapyramidal symptoms, hypotension, sedation. The patient may appear comatose with severe respiratory depression or shock from hypotension. The extrapyramidal symptoms are muscular weakness or rigidity, a generalized or localized tremor that may be characterized by the akinetic or agitation types of movements, respectively.