Continuation of Treatment With Clozapine After an Episode of Neutropenia

Risk of clozapine-associated agranulocytosis and mandatory white blood cell monitoring: Can the regulations be relaxed?

After the introduction of clozapine eight Finnish patients died after developing agranulocytosis. Clozapine was withdrawn from the market and only reintroduced with strict mandatory white blood cell monitoring as long as treatment lasts and thresholds at which clozapine must be discontinued definitively. The fear of agranulocytosis and the need for intensive blood monitoring is the single most important barrier for prescribers and patients alike and leads to underprescription of the only effective and approved medication for treatment-resistant schizophrenia. We summarize evidence that the risk of agranulocytosis is smaller than perceived at the time of reintroduction, is concentrated in the first 18 weeks of treatment, is not greater than with other antipsychotics thereafter and that frequent blood monitoring has not demonstrably decreased the rate of agranulocytosis. Therefore we propose 1) mandatory monitoring of the absolute neutrophil count (ANC) exclusively during the first 18 weeks of clozapine treatment, 2) that thereafter the prescriber and the well-informed patient decide together about further monitoring frequency, 3) that clozapine treatment must be stopped if the ANC falls below 1.0 × 109/L. Continuation of clozapine or a rechallenge are possible if prescriber and patient determine that the benefits outweigh the risks. 4) National registries which control the haematologic monitoring are unnecessary and do not help to reduce clozapine-induced agranulocytosis. They should at least be restricted to the first 18 weeks of clozapine use.

Clozapine Rechallenge or Continuation Despite Neutropenia, an Extended Follow-up of a Consecutive Quebec Case Series

BACKGROUND

Clozapine is the most efficacious antipsychotic for treatment-resistant schizophrenia. However, clozapine-induced neutropenia may warrant treatment discontinuation, hindering recovery. Several case reports describe clozapine rechallenge or continuation despite neutropenia, although many are subject to selective reporting, with incomplete information and short follow-up periods. Thus, consecutive case series, devoid of such bias, with long-term comprehensive follow-up are needed to better assess this practice. This study aimed to describe consecutively the evolution of every patient in the Québec City catchment area for whom clozapine was either reintroduced after neutropenia during a previous clozapine trial or was maintained despite a first neutropenia.

METHODS

Patients were identified through clozapine's national hematological monitoring database and their medical records between January 1, 2000, and October 22, 2017.

RESULTS

Twenty-three patients were identified, 8 continued clozapine despite neutropenia, while 15 discontinued clozapine and attempted rechallenge; among the latter, 4 patients were successfully rechallenged after agranulocytosis without the use of granulocyte colony-stimulating factors, which is the largest published consecutively. A total of 6 patients experienced further neutropenia episodes. Every patient who had a neutropenia recurrence also had a possible explanation for neutropenia other than exposure to clozapine. After a median follow-up of 4.8 years, 16 patients were still on clozapine and 3 cases discontinued because of a hematological event.

CONCLUSIONS

This study adds further data on the subject of clozapine rechallenge or continuation despite neutropenia. Clozapine rechallenge after agranulocytosis may be less perilous than first thought, but a systematic review on this specific subject is needed.