Movement disorders induced by psychiatric drugs that do not block dopamine receptors

Most movement disorders in psychiatric patients are induced by neuroleptic antipsychotic medications, all of which are dopamine D2 receptor blocking drugs. These include: acute onset disorders: dystonic reactions, akathisia and the neuroleptic malignant syndrome (NMS); non-acute onset parkinsonism; and the tardive syndromes. However, many other medications, when used at recommended doses, also induce movement disorders, with tremor being the most common. With the exception of serotonin syndrome, they are rarely as severe or disabling as the neuroleptic extrapyramidal syndromes may be. The serotonin reuptake inhibiting (SSRI) drugs are associated with the serotonin syndrome, a life-threatening disorder, but may also cause tremor and akathisia. While SSRI's have been thought to occasionally cause a tardive dyskinesia-like syndrome, this almost never occurs without prior or concurrent neuroleptic exposure as well. There also are few reliable data to support an association between antidepressants and parkinsonism. Valproic acid has been shown to cause parkinsonism, and lithium may as well, in addition to both having the well-known side effect of tremors. Myoclonus and asterixis are usually induced by toxic levels of medications but may appear with therapeutic levels, particularly with anticonvulsant mood stabilizers, and clozapine. Ataxia rarely occurs with non-toxic levels of drug, particularly anticonvulsants, benzodiazepines and lithium.