Risperidone
Class: antipsychotic – atypical
Indications (NB some may be unlicensed): schizophrenia, psychosis, behavioural/ psychological symptoms of dementia, conduct/behavioural disorders in mentally retarded, autism, mania in bipolar disorder, delirium
Contraindications/cautions: Parkinson’s disease, DLB, epilepsy, cardiovascular/ cerebrovascular disease, diabetes; caution in renal & hepatic impairment
Adverse reactions: very common: (>10%) – parkinsonism; common: insomnia, anxiety, headache, extrapyramidal symptoms; less common: drowsiness, dizziness, GI upset, sexual dysfunction, constipation, dry mouth, postural hypotension
Metabolism/clearance: metabolised by metabolising enzyme CYP3A and 2D6 mainly in the liver
Interactions:
- increased clinical effect/toxicity of risperidone (due to increased blood concentrations) may occur with some CYP metabolising enzyme inhibitors (see above) e.g. aprepitant, bupropion, clarithromycin, fluoxetine, grapefruit juice, indinavir, itraconazole, ketoconazole, nelfinavir, paroxetine, quinine, ritonavir, telapravir, voriconazole, verapamil
- decreased clinical effect/toxicity of risperidone (due to decreased blood concentrations) may occur with some CYP metabolism enzyme inducers (see above) e.g. carbamazepine, phenobarbitone, phenytoin, rifampicin, St John’s wort
- possible increased risk of extrapyramidal effects with dopamine antagonists e.g. metoclopramide
- additive hypotension may occur with antihypertensives e.g. ACEI
- additive CNS effects with other CNS depressants e.g. benzodiazepines (e.g. lorazepam), phenothiazines (e.g. chlorpromazine), opioids, alcohol
| Dosing: | ||
|---|---|---|
| oral: | dementia | initially 0.25 mg twice a day increasing to a max. of 1 mg twice a day |
| delirium | Start with 0.5 to 1 mg at bedtime and prn; if necessary increase by 0.5 to 1 mg after 2 days Mean effective dose 1.5 mg/24 hours (range 0.5 to 3 mg) | |
| Psychosis & mania | Start with 2 mg at bedtime; can increase by 2 mg at bedtime on successive days to 6 mg. Halve dose in elderly and those with severe renal/hepatic impairment | |
| subcut/rectal: | not available | |
Syringe driver: not available
Mechanism of action: antagonises serotonin and dopamine receptors in the CNS
Onset: psychosis: 1 to 2 weeks
Notes:
- lower potential for neurological adverse effects e.g. extrapyramidal effects than conventional antipsychotics
- increasingly used in acute delirium and behavioural disturbances associated with brain tumours
- at high dose (> 6 to 8 mg a day) or in the cerebrally compromised patient extrapyramidal side effects may occur
- doses can be given once daily at bedtime