HALOPERIDOL DECANOATE
Clinical safety rating: safe
Animal studies have demonstrated safety
Haloperidol decanoate is a long-acting ester prodrug of haloperidol, a typical antipsychotic. Haloperidol acts primarily as a dopamine D2 receptor antagonist in the central nervous system, particularly in the mesolimbic and mesocortical pathways. It also exhibits affinity for D1, D3, D4, sigma, and 5-HT2 receptors, but its antipsychotic efficacy is primarily attributed to D2 blockade.
| Metabolism | Haloperidol decanoate is hydrolyzed in the liver to haloperidol. Haloperidol undergoes extensive hepatic metabolism via CYP3A4 and CYP2D6, with minor contributions from other CYP enzymes. Major metabolites include reduced haloperidol and haloperidol pyridinium, which are glucuronidated and excreted in urine and feces. |
| Excretion | Renal: 40% (as metabolites; <1% unchanged); Fecal: 60% (primarily via biliary elimination). |
| Half-life | Terminal elimination half-life of haloperidol decanoate: approximately 3 weeks (range 14-28 days) due to slow release from depot and subsequent de-esterification. Steady-state achieved after 3-4 monthly doses. |
| Protein binding | 92% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 8-21 L/kg (large, indicating extensive tissue distribution; clinical meaning: high lipophilicity leading to accumulation in peripheral compartments). |
| Bioavailability | Intramuscular (decanoate): 100% (due to complete absorption from depot, but slow release); Oral: 60-70% (haloperidol base, first-pass effect). |
| Onset of Action | Intramuscular (depot): 1-2 weeks; peak plasma concentrations at 3-9 days. |
| Duration of Action | 3-4 weeks per injection; clinical effect persists for the dosing interval (monthly). |
| Molecular Weight | 530.48 |
100-200 mg intramuscular deep injection every 4 weeks. Maximum 450 mg per month.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for renal impairment. Hemodialysis does not significantly remove haloperidol. |
| Liver impairment | Child-Pugh A: No adjustment; Child-Pugh B: Reduce dose by 50%; Child-Pugh C: Contraindicated or use with extreme caution. |
| Pediatric use | Not recommended for children; safety and efficacy not established. If used: 1.5-5 mg/kg IM every 4 weeks; maximum 10 mg/kg per month. |
| Geriatric use | Initial dose 12.5-25 mg IM every 4 weeks; titrate slowly. Increased sensitivity to extrapyramidal and anticholinergic effects. |
| 1st trimester | Haloperidol decanoate is generally not recommended in the first trimester due to potential teratogenic effects. Use only if benefit outweighs risk. |
| 2nd trimester | Use cautiously; consider lower doses. Risk of extrapyramidal symptoms in neonate with chronic use. |
| 3rd trimester | Use cautiously near term; may cause neonatal extrapyramidal symptoms and withdrawal. Monitor neonate for adverse effects. |
Clinical note
CNS depressants may enhance sedative effects Can cause extrapyramidal symptoms and QT prolongation.
| Placental transfer | Haloperidol crosses the placenta. Transfer is documented, with fetal concentrations approximately equal to maternal concentrations after chronic administration. |
| Breastfeeding | Haloperidol is excreted into breast milk in low concentrations. The long-acting decanoate formulation may result in sustained exposure. Monitor infant for sedation, irritability, and abnormal movements. Use with caution, weighing benefits of therapy against potential risks. |
■ FDA Black Box Warning
Increased mortality in elderly patients with dementia-related psychosis. Haloperidol decanoate is not approved for the treatment of dementia-related psychosis.
| Common Effects | Tourette's syndrome |
| Serious Effects |
Comatose statesCNS depression from alcohol or other depressantsParkinson's diseaseKnown hypersensitivity to haloperidol or decanoateSevere toxic central nervous system depression
| Precautions | QT prolongation and torsades de pointes (dose-related; use caution with other QT-prolonging agents); neuroleptic malignant syndrome; tardive dyskinesia; extrapyramidal symptoms (especially acute dystonias); stroke risk in elderly with dementia; orthostatic hypotension; seizure threshold reduction; increased mortality in elderly with dementia; caution in patients with cardiovascular disease, epilepsy, and renal impairment. |
| Food/Dietary |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited data; potential risk of congenital malformations (case reports of limb defects). Second/third trimester: Risk of extrapyramidal symptoms and withdrawal in neonates (e.g., agitation, hypertonia). Overall risk not definitively established; avoid if possible. |
| Fetal Monitoring | Monitor maternal vital signs, EPS, QTc interval (ECG). Fetal: ultrasound for growth and anomalies; neonatal assessment for EPS and withdrawal post-delivery. |
| Fertility Effects | May increase prolactin levels causing menstrual irregularities, galactorrhea, and reduced fertility in females. In males, potential for erectile dysfunction and decreased libido. Effects reversible upon discontinuation. |
| Avoid grapefruit and grapefruit juice as it may increase haloperidol levels. Avoid alcohol as it can worsen CNS depression. No other significant food interactions. |
| Clinical Pearls | Administer deep IM in gluteal muscle using Z-track technique; do not massage injection site. Use a 21G needle for aspiration. Do not exceed 100 mg (2 mL) per injection site. Initiate with oral haloperidol to assess tolerability before switching to decanoate. Wait at least 4 weeks before adjusting dose due to long half-life. Avoid in patients with QTc prolongation or history of neuroleptic malignant syndrome. |
| Patient Advice | This medication is a long-acting injection given every 2-4 weeks. · Do not miss appointments as effects last for weeks. · May cause drowsiness, dizziness, or blurred vision; avoid driving until you know how it affects you. · Report any muscle stiffness, fever, confusion, or irregular heartbeat to your doctor immediately. · Avoid alcohol and grapefruit juice while on this medication. · Do not stop suddenly; withdrawal may cause nausea, sweating, or insomnia. |