Clozapine therapeutic drug monitoring can be useful in certain circumstances, but is not required for routine management, for example:
- If the patient’s smoking status changes
- To monitor compliance
- In poor responders after an adequate trial especially prior to consideration of augmentation strategies
- If dose reduction is being contemplated
- To diagnose dose-related side effects
- If a drug interaction is suspected
- Non-urgent investigation of suspected overdose
- Measuring baseline levels during successful treatment to use as a reference point
- For patients on long term high dose who have no evidence of previous levels as part of their annual physical review
Side effects that are thought to be dose-related include; sedation, dizziness, hypersalivation, tachycardia, postural hypotension, constipation and seizures. Often these can be avoided/minimised by careful and slow dose escalation or alleviated by reducing the dose.
As a rule, treat the patient – not the level