NHS Greater Glasgow & Clyde Area Drug and Therapeutics Committee
Greater Glasgow and Clyde Medicines
Medicines Update

Clozapine Supply and Missed Doses in Acute

Updated July 2020

Key messages:

  • Acute hospital sites in NHSGGC do not stock clozapine
  • Clozapine is generally supplied from Leverndale Pharmacy
  • Leverndale Pharmacy should be contacted (including out of hours) when patients on clozapine are admitted to an acute hospital to inform of admission, confirm dose and arrange supply (if required). Leverndale Pharmacy should also be contacted when patients are discharged.
  • If a patient misses clozapine for more than 48 hours, it must be re-titrated to their original dose on advice of the mental health (MH) team

Clozapine is the gold standard treatment for treatment-resistant schizophrenia. It is also licensed for those intolerant of other antipsychotics and for psychosis in Parkinson's Disease. Due to the potential risk of neutropenia and agranulocytosis, regular full blood counts (FBCs) are required as well as registration with a clozapine patient monitoring service.

How to contact Leverndale Pharmacy?

When patients on clozapine are admitted to an acute hospital, ward staff should contact Leverndale Pharmacy at the earliest opportunity to inform of admission, confirm the current dose of clozapine and to arrange a supply of clozapine if the patient hasn't brought their own in. During working hours, contact Leverndale Pharmacy (on 211 6525) and out with working hours and at weekends, contact the on call MH pharmacy team (via switchboard).

What are the key issues to consider when a patient is admitted on clozapine?

  • Medicines Reconciliation

Clozapine will appear in the patient's ECS as an 'out of practice drug' only if the GP practice has added it. There is a risk that clozapine may not appear in every patient's ECS, therefore, using other sources to ensure accurate medicines reconciliation is essential, including checking the Mental Health Summary within Clinical Portal for a clozapine alert.

  • Last dose taken prior to admission

If clozapine is missed for more than 48 hours it should be re-titrated on advice from MH starting at 12.5mg once daily. Serious adverse effects including tachycardia, postural hypotension, myocarditis and seizure activity can occur if a full treatment dose is administered after a break in treatment. Seek advice from MH.

  • Supply

Use patient's own or arrange an individual patient supply from Leverndale Pharmacy. Always transfer clozapine supply between wards or hospitals with the patient.

  • Presenting complaint

Consider if the patient's presentation may be related to clozapine, e.g. bowel obstruction, cardiac symptoms, blood dyscrasias, aspiration pneumonia; advice must be sought from MH prior to prescribing clozapine.

  • Side effects

Dose-related side effects that may require dose reduction include constipation, hypersalivation, sedation and seizures. Seek advice from MH.

  • Smoking

Induces the metabolism of clozapine, therefore, stopping smoking during an inpatient stay can increase clozapine dose-related adverse effects and may require dose reduction. Seek advice from MH.

  • Bloods

It is essential to check FBCs during admission. If there are any abnormalities with FBC parameters, seek advice from MH.

  • Interactions

Clozapine is contraindicated with any medicine known to cause myelosuppression. Caution is also advised with current use of any QTc prolonging medicines. For general information on QT prolongation, refer to the Medicines Update Extra bulletin here.

For more information, refer to the Managing clozapine patients in acute hospitals guideline in the Adult Therapeutics Handbook. MH services are always available for advice.


Originally published 20/08/18 and updated on 28/07/20. Medicines Update blogs are correct at the time of publication.