237 - Switching from other antipsychotics

Switching from other antipsychotics

Schizophrenia and related psychoses CHAPTER 1 Adverse effects Sedation, hypersalivation and hypotension are common at the start of treatment. These effects can usually be managed (see section on clozapine: common adverse effects in this chapter) but require particular attention in community titration. Consider regular systematic assessment of adverse effects using a recognised scale such as the GASS for Clozapine. The formal carer (usually the community psychiatric nurse) should inform the prescriber if: ■ ■temperature rises above 38°C (this is very common and is not a good reason, on its own, for stopping clozapine) ■ ■pulse is >100bpm (also common and not, on its own, a reason for stopping, but may sometimes be linked to myocarditis) ■ ■postural drop of >30mmHg ■ ■patient is clearly over-­sedated ■ ■any signs of constipation (initiate laxatives early) ■ ■flu-­like symptoms (malaise, fatigue, etc.) ■ ■chest pain, dyspnoea, tachypnoea ■ ■any other adverse effect that is intolerable ■ ■changes in smoking habit. The patient should be reviewed at least once a week for the first month to assess mental and physical state. Recommended additional monitoring Baseline 1 month 3 months 4–6 months 12 months Weight/BMI/waist Weight/BMI/weight Weight/BMI/ waist Weight/BMI/waist Weight/BMI/waist Plasma glucose and lipids Plasma glucose and lipids Plasma glucose and lipids Plasma glucose and lipids LFTs LFTs Monitor CRP, CK, troponin weekly in the first four weeks of treatment or if temperature is above 38°C (see section on clozapine and myocarditis). CK, B-­natriuretic peptide and echocardiogram should be used to confirm or rule out myocarditis if CRP and troponin are raised above thresholds.6 Switching from other antipsychotics ■ ■The switching regimen will be largely dependent on the patient’s mental state. ■ ■Consider potential additive adverse effects of antipsychotics (e.g. hypotension, sedation, effect on QTc interval). ■ ■Consider drug interactions (e.g. some SSRIs may increase clozapine levels). ■ ■Other antipsychotics and clozapine may be cross-­tapered with varying degrees of caution. ECG monitoring is prudent when clozapine is co-­prescribed with other drugs known to affect QT interval. (Pimozide and ziprasidone should be stopped before clozapine is started.)