Smoking bans and clozapine levels

The smoking ban implemented in the UK this July (Campion et al, 2008) will greatly affect psychiatric in-patients, of whom as many as 74% are smokers (Meltzer et al, 1996). Plasma concentrations of certain psychotropics are known to be affected by smoking status. Smokers are usually prescribed higher doses than non-smokers and abrupt smoking cessation will lead to high plasma concentrations and potentially more side-effects.

Clozapine plasma concentrations can rise 1.5 times in the 2–4 weeks following smoking cessation (de Leon, 2004) and in some instances by 50–70% within 2–4 days. If baseline plasma concentrations are higher – particularly over 1 mg/litre – the plasma concentration may rise dramatically owing to non-linear kinetics. If patients smoking more than 7–12 cigarettes per day while taking clozapine decide to quit, the dose may need to be reduced by 50% (Haslemo et al, 2006).

Although patients may not quit during an admission their access to cigarettes may be limited, depending on leave status or other practicalities (e.g. availability of staff to escort them off the ward). The as-required prescription of nicotine replacement therapy, although strictly speaking off-license, may help cravings but it has no effect on clozapine plasma concentration.

All patients should be forewarned that in-patient settings are now smoke-free, and clinicians need to clarify and record smoking status on admission. They will also need to monitor clozapine plasma concentrations in smokers closely during admissions and shortly after discharge. All UK assays are performed at the Toxicology Unit, Kings’ College Hospital, London, and electronic access to results is possible after registration ([email protected]). Savings made by clozapine dose reductions will mitigate the additional costs incurred!

References

Campion, J., Checinski, K., Nurse, J., et al (2008) Smoking by people with mental illness and benefits of smoke-free mental health services. Advances in Psychiatric Treatment, 14, 217–228.[Abstract/Free Full Text]

de Leon, J. (2004) Atypical antipsychotic dosing: the effect of smoking and caffeine. Psychiatric Services, 55, 491–493.[Free Full Text]

Haslemo, T., Eikeseth, P. H., Tanum, L., et al (2006) The effect of variable cigarette consumption on the interaction with clozapine and olanzapine. European Journal of Clinical Pharmacology, 62, 1049–1053.[CrossRef][Medline]

Meltzer, H., Gill, B., Petticrew, M., et al (1996) Economic Activity and Social Functioning of Residents with Psychiatric Disorders (OPCS Surveys of Psychiatric Morbidity in Great Britain, Report 6). TSO (The Stationery Office).

Mohammed Ashir and Louise Petterson