New guidance on monitoring blood levels of clozapine

The College’s Psychopharmacology Committee wishes to draw attention to new Medicines and Healthcare products Regulatory Agency (MHRA) guidance on monitoring of blood levels of clozapine in certain clinical situations, including when a patient who is receiving clozapine stops smoking cigarettes or when other medicines may interact to increase blood clozapine levels.

The guidance also comments on targeted monitoring of blood levels of other antipsychotic drugs where such facilities are available.

The new MHRA guidance –  Clozapine and other antipsychotics: monitoring blood concentrations for toxicity – was written with support from the Psychopharmacology Committee.

Dr Sarah Branch, Director of Vigilance and Risk Management of Medicines at the MHRA, said:

“We are advising healthcare professionals to monitor blood clozapine levels for toxicity in patients taking clozapine in certain clinical situations.

“Blood clozapine level monitoring should be carried out in addition to the required blood tests to manage the risk of agranulocytosis (lowered white blood cell count).

“We are also advising healthcare professionals that where testing and reference values are available, blood level monitoring of other antipsychotics for toxicity may also be helpful in certain circumstances.

“Patients taking clozapine or another antipsychotic should continue their treatment as advised by their doctor. Healthcare professionals and patients are asked to please report any suspected side effects from clozapine or any other medicine via the Yellow Card scheme.”

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