Haloperidol
Class: antipsychotic – butyrophenone
Indications (NB some may be unlicensed): psychotic disorders, acute alcoholism, intractable nausea and vomiting, neuroleptanalgesia, intractable hiccup; delirium in palliative care
Contraindications/cautions: hepatic encephalopathy, epilepsy, dementia, Parkinson’s disease, DLB; caution in cardiac disease (QT prolongation)
Adverse reactions: common: extrapyramidal symptoms (usually at 5 to 20 mg/24 hours) e.g. oculogyric crisis, dystonia, tremor, abnormal movements, restlessness – may be less with parenteral route; less common: hyperprolactinaemia, dry mouth, sedation, arrhythmias, QT prolongation, dizziness, sedation, visual disturbance
Metabolism/clearance: metabolised by metabolising enzyme CYP2D6 and CYP3A mainly in the liver
Interactions:
- increased clinical effect/toxicity of haloperidol (due to increased blood concentrations) may occur with some CYP metabolising enzyme inhibitors (see above) e.g. aprepitant, bupropion, clarithromycin, fluoxetine, grapefruit juice, itraconazole, ketoconazole, paroxetine, valproate, voriconazole
- decreased clinical effect/toxicity of haloperidol (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
- increased clinical effect/toxicity of some drugs (due to increased blood concentrations of them) may occur with haloperidol due to metabolising enzyme inhibition by haloperidol e.g. amitriptyline, codeine (decreased morphine concentrations so decreased clinical efficacy of codeine), haloperidol, metoclopramide, nortriptyline, promethazine, tamoxifen (decreased endoxifen (active metabolite) concentrations so decreased clinical effects)
- additive CNS effects with other CNS depressants e.g. benzodiazepines (e.g. lorazepam), phenothiazines (e.g. chlorpromazine), tricyclic antidepressants (e.g. amitriptyline), opioids, alcohol
- enhanced extrapyramidal side-effects may occur with lithium
- additive anticholinergic effects (e.g. dry mouth, urinary retention) may occur with other drugs which have anticholinergic effects e.g. cyclizine, amitriptyline, phenothiazines
| Dosing: | |||
|---|---|---|---|
| oral: parenteral = 3:2 (bioavailability variable 40 to 85% orally) | |||
| nausea/vomiting | delirium (see notes) | ||
| oral: | 1.5 to 3 mg once a day | oral: | 1.5 to 20 mg per 24 hours |
| subcut: | 1 to 2 mg/24 hours | subcut: | 1 to 15 mg/24 hours |
| iv: | 2 to 5 mg (at 1 mg/minute) | ||
| Intractable hiccup: | 1.5 to 3 mg twice to 3 times daily – can reduce to 0.5 to1 mg 3 times daily once controlled | ||
Syringe driver: see syringe driver compatibility chart
130 Te Puka Manaaki Pairuri o Aotearoa – Putanga Tuatahi
Mechanism of action: nausea/vomiting – blocks dopamine receptors in the chemo-receptor trigger zone thus blocking input into the vomiting centre; delirium – may rebalance the unbalanced cholinergic/dopaminergic systems seen in delirium
Peak effect: oral: 2 to 6 hours im/subcut: 20 minutes
Duration: up to 24 hours
Notes:
- useful as an antiemetic where causes of nausea and vomiting are biochemical imbalance or toxins
- particularly useful in opioid induced nausea and vomiting. It may be given as a single oral dose at night. Doses greater than 3 mg daily add no benefit. Start with 0.5 mg in elderly
- delirium: The primary pharmacological intervention for delirium is to tranquillise (to control psychotic features). Occasionally sedation (to induce sleep) is an additional requirement. (See Delirium page)