2 Prescribing points
The patient should be fully involved in decisions about treatment, including the possibility of psychological, occupational and social therapies. It is important to bear the following points in mind when starting antipsychotic treatment:
- Use antipsychotics within their licensed indications and doses, except on specialist advice
- Use only one antipsychotic at any one time except when switching from one antipsychotic to another or on specialist advice
- Except in very specific instances, do not use an antipsychotic for treating behavioural and psychological symptoms of dementia - see Elderly patients with dementia
- Start treatment with a dose at the lower end of the licensed dose range
- Advise the patient that improvement may take several days to some weeks. The antipsychotic medicine should be continued, at optimum dose, for 4–6 weeks before assessing response to treatment. Patients should be closely monitored during this period
- It is helpful to discuss with the patient possible adverse effects of antipsychotic treatment such as movement disorders (extrapyramidal side effects), consequences of raised prolactin (including effects on sexual function), and metabolic changes; this can help with adherence to treatment (see Adherence to treatment) and lay the foundation for future discussion especially about adverse effects that patients might be reticent to talk about. The patient information leaflet can be used to prompt discussion of adverse effects.
- The dose of some antipsychotics may need to be adjusted in hepatic impairment to lower the risk of adverse effects such as coma. Further, some antipsychotics, especially phenothiazines, are hepatotoxic and their use in severe hepatic impairment can lead to coma.
- Withdrawal effects may occur, especially if the antipsychotic is discontinued abruptly after prolonged use
- Antipsychotics should be used with caution and smaller doses selected in marked renal impairment to prevent cerebral toxicity. In renal insufficiency, dose reduction may be necessary especially if the drug is excreted by the kidney (eg amisulpride and sulpiride).
- Use an antipsychotic judiciously in the elderly, with careful and individual evaluation of likely benefits and risks—the risk of adverse events is greater in frail, elderly people, especially in the presence of other disorders (eg markedly impaired renal function and immobility)
- Use of multiple medicines (‘polypharmacy’) for diverse conditions associated with old age increases the risk of adverse effects and drug–drug interactions
- Special care is required when prescribing an antipsychotic to a woman of child-bearing potential and to the elderly
The metabolism of some drugs is affected by smoking and by intake of caffeine. Aromatic hydrocarbons in tobacco smoke induce the isoenzyme CYP1A2, thus speeding up the metabolism of clozapine. Caffeine by contrast reduces CYP1A2 metabolism of clozapine, albeit modestly. Therefore, smoking promotes removal of clozapine from the body while caffeine can reduce its elimination. It follows that cessation of smoking or possibly changes in caffeine intake can alter the dose requirement of clozapine. Smoking-related induction of enzyme activity also hastens the metabolism of olanzapine, but the dose does not usually need to be altered.
Before and during treatment with an antipsychotic drug, it is important to evaluate patients’ physical health and promptly identify:
- metabolic adverse changes (eg raised blood glucose and cholesterol, dyslipidaemia)
- endocrine effects (changes to prolactin levels, features of diabetes and diabetic ketoacidosis)
- liver function abnormality
- cardiovascular disorders (eg adverse changes in cardiac conduction and blood pressure)
- blood disorders
- weight changes
- movement disorders.
Monitoring guidelines, including recommendations from NICE, should be adhered to.
At each consultation, record carefully the patient’s response to the treatment (i.e. changes in symptoms). Enquire in detail into adverse effects; a structured approach for assessing side-effects is more likely to reveal the full spectrum of unwanted effects. An open question (eg ‘How are you getting on with your medicine?’) is less likely to unearth all the effects that worry the patient. Check adherence to the prescribed regimen. Adverse effects such as dysphoria and sexual dysfunction can reduce adherence to antipsychotic treatment.
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