Dystonia, antipsychotics causing

Among the most significant adverse reactions associated with the antipsychotic dm are the extrapyramidal effects. The term extrapyramidal effects refers to a group of adverse reactions occurring on the extrapyramidal portion of the nervous system as a result of antipsychotic drains. This part of the nervous system affects body posture and promotes smooth and uninterrupted movement of various muscle groups. Antipsychotics disturb the function of the extrapyramidal portion of the nervous system, causing abnormal muscle movement. Extrapyramidal effects include Parkinson-like symptoms (see Chap. 29), akathisia, and dystonia (see Display 32-1). 

Regarding neuroleptic-induced dystonias, it is well known that typical neuroleptics cause catalepsy in rats and movement disorders in man. By contrast, the atypical neuroleptics clozapine and sulpiride have a low propensity to cause movement disorders in man even though they have established antipsychotic effects. These atypical neuroleptics, unlike many of the typical neuroleptics, have a low affinity for sigma receptors which lends support to the hypothesis that the dystonias produced by typical... 

Burke, R., Fahn, S., Jankovic, J., Marsden, C. D., Lang, A. E., Gollomp, S., et al. (1982). Tardive dystonia Late-onset and persistent dystonia caused by antipsychotic drugs. 

Burke RE, Fahn S, Jankovic J, Marsden CD, Lang AE, Gollomp S, Ilson J. Tardive dystonia late-onset and persistent dystonia caused by antipsychotic drugs. Neurology 1982 32(12) 1335-46. 

Loxapine (10 mg b.i.d.) is indicated for the treatment of psychotic disorders. It exerts its antipsychotic effects in part by blocking postsynaptic dopamine receptors. It causes moderate sedation, possesses anticholinergic properties, and produces extensive movement disorders such as akathi-sia, dystonia, parkinsonism, tardive dyskinesia, and neuroleptic malignant syndrome. 

CNS Scopolamine is standard therapy for motion sickness this drug is one of the most effective agents available for this condition. A transdermal patch formulation is available. Benztropine, biperiden. and trihexyphenidyl are representative of several antimuscarinic agents used in parkinsonism. Although not as effective as levodopa (see Chapter 28), these agents may be useful as adjuncts or when patients become unresponsive to levodopa. Benztropine is sometimes used parenterally to treat acute dystonias caused by antipsychotic medications. 

Contrary to the usual activity of antipsychotics, clozapine exhibits regional specific anti-dopaminergic profile having, relatively mild antagonism on the extrapyramidal dopaminergic action and this could be responsible for its low propensity to produce extrapyramidal side effects e.g., dystonias, tardive dyskinesia. It also causes greater blockade of dopamine D-1 receptors and however, it is not yet established whether such action precisely contributes to its antipsychotic therapeutic activity. 

The authors of the report suggest that this reaction was possibly caused by the additive dystonic effects of the loxapine and sumatriptan, despite the presence of the benzatropine. Dystonia is not an uncommon extrapyramidal reaction associated with antipsychotics, and neck stiffness and dystonia are recognised adverse effects of sumatriptan, but of low incidence. This seems to be the first and only report of this apparent interaction, and therefore its general significance is unclear. 

If the central antimuscarinic effects caused by the use of antimuscarinic drugs are not clearly recognised for what they are, there is the risk that antipsychotics may be prescribed to treat them. Many antipsychotics also have antimuscarinic adverse effects so that matters are simply made worse. If the patient then demonstrates dystonias, akathisia, tremor and rigidity, even more antimuscarinics may be added to control the extrapy-... 

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