Reversible neurotoxicity induced by a combination of clozapine and lithium: a case report

A combination of clozapine and lithium can be used in the treatment of refractory schizophrenia, schizoaffective disorder and bipolar disorder with rapid cycling. We report a patient with refractory bipolar disorder who developed side-effects after combination therapy with clozapine and lithium at usual therapeutic dosages. Reversible neurotoxicity developed twice during the therapeutic course, once with the restarting of lithium, the other with increasing the dose of lithium, despite the lithium concentrations being less than 0.5 mEq/l. Neurotoxicity manifested as ataxia, coarse tremor, myoclonus, facial spasm and increased deep tendon reflex. While the mechanism causing toxicity is not clear, interaction between the serotonergic effect of clozapine and lithium may be the cause. This report is evidence that a combination of clozapine and lithium may increase the risk of neurotoxicity. We suggest the need to keep clozapine and lithium at lower dosages and closely monitor their side-effects as necessary when these drugs are used concomitantly.