Are clozapine patients at risk for blood dyscrasias with concomitant tamiflu use?

Flu vaccination is the best protection against seasonal flu; however, as mutated strains of the flu develop and/or unvaccinated people are exposed to the wild virus, antiviral prophylaxis becomes more important. High-risk patients, such as those institutionalized, are particularly vulnerable to adverse drug events and possibly even more so during the course of active viral infection. As clinicians pursue antiviral treatment, it is important to know the potential risks of prescribing concurrent medication regimens. The objective of this study was to contribute to the evolving literature by evaluating the occurrence of blood dyscrasias with concurrent use of oseltamivir and clozapine (a drug used to treat refractory schizophrenia). This study was a retrospective chart review conducted at a 240-bed New York State mental health facility during an influenza outbreak where oseltamivir was distributed to the vast majority of inpatients. The records of 32 patients treated with concurrent oseltamivir and clozapine were assessed for alterations in white blood count and/or absolute neutrophil count at designated periods and compared to baseline lab values. A repeated measures ANOVA was used to analyze the data.

No changes in white blood cell were noted as a result of concomitant oseltamivir and clozapine therapy in the study sample; however, there were statistically significant differences between the absolute neutrophil count from before oseltamivir and the two time periods following oseltamivir administration. Cautions are detailed regarding concomitant use; however, proactive clozapine discontinuation prior to antiviral treatment is unwarranted.