A case of recurrent seizures: Drug-drug interaction between low-dose clozapine and extended-release bupropion

Optimizing antidepressant and clozapine co-prescription in clinical practice: A systematic review and expert recommendations

OBJECTIVES

To synthesize the information relevant for clinical practice on clozapine-antidepressant co-prescription concerning pharmacokinetic drug-drug interactions (DDI), adverse drug reactions (ADRs) associated with the co-prescription, antidepressant add-on for clozapine-resistant symptoms and antidepressant add-on for clozapine-induced ADRs.

METHODS

Articles were identified with MEDLINE, Web of Sciences and PsycINFO search from inception through April 2023. Data were synthesized narratively.

RESULTS

ADRs are most often induced by the co-prescription of antidepressants that inhibit CYP enzymes (fluvoxamine, fluoxetine, paroxetine). Fluvoxamine add-on is hazardous because of its potent inhibition of clozapine metabolism and has few indications (lowering daily number of clozapine tablets, reducing norclozapine-induced metabolic disturbances and other dose-dependent clozapine-induced ADRs). ADR frequency may be reduced by therapeutic drug monitoring and knowledge of other factors impacting clozapine metabolism (pneumonia, inflammation, smoking, etc.). Improvement of negative symptoms is the most documented beneficial effect of antidepressant add-on for clozapine-resistant psychotic symptoms. The add-on antidepressant should be chosen according to its safety profile regarding DDI with clozapine: antidepressants inhibiting clozapine metabolism or increasing the anticholinergic load should be avoided. Other indications of antidepressant add-on (affective or obsessive compulsive symptoms, sialorrhea, and enuresis) are poorly documented.

CONCLUSION

Antidepressant add-on to clozapine is associated with potential benefits in clozapine users as this strategy may contribute to reduce the burden of clozapine-resistant symptoms or of clozapine-induced ADRs. Further studies are needed to determine whether antidepressant add-on can reduce the risk of clozapine discontinuation.

Bupropion With Clozapine: Case Reports of Seizure After Coadministration

BACKGROUND

Clozapine is more effective than other atypical antipsychotics for treatment resistant schizophrenia, but has serious side effects. Clozapine has an estimated cumulative seizure risk of 10% in patients treated for 3.8 years. Bupropion can also induce seizures and its estimated risk is 0.4% at recommended doses. While some risk factors for seizures are known, much remains unknown about predicting seizure risk. Cases: We present 2 cases of seizures in patients treated with clozapine and bupropion without a seizure history. In the first case, a patient with schizoaffective disorder treated with dual antipsychotic therapy had a witnessed generalized tonic-clonic seizure. With the exception of bupropion/naltrexone which was started 2.5 months prior for weight loss, she had not had any recent medication changes. In the second case, a patient with schizoaffective disorder was treated with clozapine and was prescribed bupropion SR for smoking cessation for an extended duration. He had cut back on cigarette use in the 2 months prior to reporting "spells." The neurologist's assessment was probable epileptic seizures which resolved after the bupropion was stopped and divalproex was started for seizure prophylaxis.

CONCLUSION

Clozapine and bupropion are known to lower the seizure threshold, but little information is available regarding the risk when used in combination. It is unclear whether these agents, when used in combination, have additive seizure risk or possible synergistic effects. Bupropion should be used cautiously in patients treated with clozapine. Safer agents that do not lower the seizure threshold should be utilized whenever possible.