PERPHENAZINE
Clinical safety rating: safe
Animal studies have demonstrated safety
Perphenazine is a typical antipsychotic that exerts its effects by blocking postsynaptic dopamine D2 receptors in the brain, particularly in the mesolimbic pathway. It also has antagonistic activity at alpha-adrenergic, histaminergic, and muscarinic receptors.
| Metabolism | Primarily hepatic via CYP2D6, with minor contributions from CYP3A4 and CYP1A2. |
| Excretion | Perphenazine is extensively metabolized in the liver, primarily via CYP2D6, and eliminated predominantly as metabolites in urine (approximately 70%) and feces (about 30%). Less than 1% is excreted unchanged in urine. |
| Half-life | The terminal elimination half-life of perphenazine is approximately 8–12 hours in adults with normal hepatic function. This supports twice-daily dosing for maintenance therapy. In elderly patients or those with hepatic impairment, half-life may be prolonged. |
| Protein binding | Perphenazine is approximately 90–95% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | The volume of distribution (Vd) is approximately 10–20 L/kg, indicating extensive tissue distribution and high lipophilicity. This large Vd explains its long elimination half-life and accumulation in brain tissue. |
| Bioavailability | Oral bioavailability is approximately 40–50% due to extensive first-pass metabolism. Intramuscular bioavailability is near 100%; intravenous administration yields complete bioavailability. |
| Onset of Action | Oral: 30–60 minutes; intramuscular (IM): 10–30 minutes; intravenous (IV): 5–10 minutes. The onset of antipsychotic effect may require days to weeks. |
| Duration of Action | Duration of effect for a single oral dose is approximately 6 hours for acute effects (e.g., antiemetic action), but antipsychotic effects are sustained over 24 hours with chronic dosing. The IM route provides a longer duration (6–12 hours) due to slower absorption. |
Oral: 4-16 mg 2-4 times daily; maximum 64 mg/day. Intramuscular: 5-10 mg every 6 hours; maximum 30 mg/day. Intravenous: 1-5 mg slow IV every 6 hours; maximum 10 mg/day.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment required for renal impairment. Use with caution in severe renal dysfunction. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50%. Child-Pugh Class C: Use with caution; reduce dose by 75% or avoid. |
| Pediatric use | Children (≥12 years): 2-4 mg orally 3-4 times daily; maximum 32 mg/day. Intramuscular: 2-5 mg every 6 hours; maximum 15 mg/day. Children (6-12 years): Not recommended due to limited data. |
| Geriatric use | Initial oral dose: 2-4 mg 2-3 times daily; increase slowly. Maximum 32 mg/day. Use lowest effective dose due to increased sensitivity to extrapyramidal effects and orthostatic hypotension. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants may enhance sedative effects Can cause extrapyramidal symptoms and neuroleptic malignant syndrome.
| Breastfeeding | Perphenazine is excreted into breast milk. The milk-to-plasma (M/P) ratio is approximately 0.7-0.8. Infant exposure is low (relative infant dose ~2-4% of maternal weight-adjusted dose). Monitor infant for drowsiness, irritability, or EPS. Benefits of breastfeeding should be weighed against potential risks. |
| Teratogenic Risk | Perphenazine is a phenothiazine antipsychotic. First trimester: Human data limited; case reports suggest possible minor malformations but no clear pattern. Second and third trimesters: Exposure may cause extrapyramidal symptoms (EPS) and/or withdrawal in the neonate, including agitation, hypertonia, hypotonia, tremor, somnolence, and feeding difficulty. Overall risk not clearly established. FDA Pregnancy Category C. |
■ FDA Black Box Warning
Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Perphenazine is not approved for the treatment of dementia-related psychosis.
| Common Effects | Extrapyramidal symptoms |
| Serious Effects |
["Hypersensitivity to perphenazine or any component","Coma or severe CNS depression","Bone marrow suppression","Subcortical brain damage","Parkinson's disease (relative contraindication)","Concurrent use with high doses of other CNS depressants"]
| Precautions | ["Risk of tardive dyskinesia with prolonged use","Neuroleptic malignant syndrome (NMS)","QT prolongation and arrhythmias","Leukopenia/neutropenia/agranulocytosis","Seizure threshold lowering","Hyperprolactinemia","Drowsiness and impaired judgment","Orthostatic hypotension","Anticholinergic effects (constipation, dry mouth, blurred vision)"] |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of EPS or tardive dyskinesia. Monitor fetal growth if used chronically. In neonates, monitor for EPS, sedation, and withdrawal symptoms for 48-72 hours after delivery. Consider therapeutic drug monitoring if available. |
| Fertility Effects | May cause hyperprolactinemia, potentially leading to menstrual irregularities, galactorrhea, and impaired fertility. Reversible upon dose reduction or discontinuation. No known direct effect on sperm or oocyte quality. |