PERPHENAZINE AND AMITRIPTYLINE HYDROCHLORIDE
Clinical safety rating: safe
CNS depressants may enhance sedative effects Can cause extrapyramidal symptoms and neuroleptic malignant syndrome.
Perphenazine is a phenothiazine antipsychotic that blocks postsynaptic dopamine D2 receptors in the mesolimbic system, with additional antagonism at serotonin 5-HT2, alpha-1 adrenergic, histamine H1, and muscarinic M1 receptors. Amitriptyline is a tricyclic antidepressant that inhibits serotonin and norepinephrine reuptake, also antagonizing histamine H1, alpha-1 adrenergic, and muscarinic M1 receptors.
| Metabolism | Perphenazine is extensively metabolized in the liver via CYP2D6, CYP3A4, and CYP1A2; amitriptyline is metabolized via CYP2D6, CYP2C19, and CYP3A4 to nortriptyline, its active metabolite. |
| Excretion | Perphenazine: renal (0.5-2% unchanged), hepatic metabolism and biliary/fecal elimination (major). Amitriptyline: renal (<5% unchanged, 30-50% as metabolites), biliary/fecal (significant). Combined: ~70-80% renal (metabolites), ~20-30% fecal. |
| Half-life | Perphenazine: ~9-12 hours (range 8-20 h). Amitriptyline: ~15-24 hours (range 10-50 h). Clinical context: Steady-state reached in 3-10 days; amitriptyline's active metabolite nortriptyline has T½ ~18-35 h. |
| Protein binding | Perphenazine: ~90-95% bound (albumin, alpha1-acid glycoprotein). Amitriptyline: ~95-96% bound (albumin, alpha1-acid glycoprotein, lipoproteins). |
| Volume of Distribution | Perphenazine: ~10-20 L/kg (large, extensive tissue distribution). Amitriptyline: ~15-20 L/kg (very large, high tissue binding). Clinical meaning: High Vd indicates extensive distribution into tissues, poor dialyzability, and long washout period. |
| Bioavailability | Oral: Perphenazine ~40% (first-pass metabolism); Amitriptyline ~30-60% (first-pass metabolism; range 31-61%). |
| Onset of Action | Oral (tablet): Antidepressant/antipsychotic effect: 1-2 weeks for mood improvement; sedative effect: 30-60 minutes. IM (if available): 10-30 minutes for sedation. |
| Duration of Action | Perphenazine: 6-12 hours (antipsychotic effect). Amitriptyline: 24-48 hours (antidepressant effect); sedative effect persists 6-8 hours per dose. Note: Continuous therapy needed for full therapeutic effect. |
Oral: Perphenazine 2-4 mg with amitriptyline 10-50 mg, administered 3-4 times daily. Maximum daily dose: perphenazine 24 mg, amitriptyline 150 mg.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment required; use caution in severe renal impairment. For GFR <10 mL/min, consider reducing dose by 50%. |
| Liver impairment | Contraindicated in severe hepatic impairment. In Child-Pugh Class A: reduce dose by 50-75%. In Child-Pugh Class B: reduce dose by 75% or consider alternative. In Child-Pugh Class C: avoid use. |
| Pediatric use | Not recommended for children under 12 years. For adolescents 12-17 years: initiate at perphenazine 2 mg with amitriptyline 10 mg twice daily; titrate slowly based on response and tolerability, maximum perphenazine 16 mg/day, amitriptyline 100 mg/day. |
| Geriatric use | Initiate at low end of dosing range: perphenazine 1-2 mg with amitriptyline 10-25 mg two to three times daily. Maximum recommended: perphenazine 12 mg/day, amitriptyline 75 mg/day. Monitor for orthostatic hypotension, anticholinergic effects, and sedation. |
| 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.
| FDA category | Animal |
| Breastfeeding | Amitriptyline excreted in breast milk; M/P ratio approx 0.8-1.5. Perphenazine present in breast milk; M/P ratio not well defined. American Academy of Pediatrics considers amitriptyline compatible with breastfeeding; monitor infant for drowsiness, poor feeding. |
| Teratogenic Risk | Perphenazine: Limited human data; animal studies show fetal toxicity at high doses. Generally considered low risk but avoid in 1st trimester if possible. Amitriptyline: Crosses placenta; associated with transient neonatal withdrawal syndrome (irritability, tachyapnea) if used near term. Third trimester exposure may cause persistent pulmonary hypertension of the newborn (PPHN). |
■ FDA Black Box Warning
Increased risk of suicidal thinking and behavior in children, adolescents, and young adults with depression and other psychiatric disorders; not approved for use in pediatric patients.
| Common Effects | Extrapyramidal symptoms |
| Serious Effects |
["Hypersensitivity to perphenazine, amitriptyline, or any component","Concomitant use with MAOIs or within 14 days of discontinuation","Recent myocardial infarction","QT prolongation or history of arrhythmias","Severe hepatic impairment","Narrow-angle glaucoma","Urinary retention","Concurrent use of drugs that prolong QT interval"]
| Precautions | ["Anticholinergic effects (e.g., urinary retention, constipation, blurred vision)","Sedation and impaired cognitive/motor function","Cardiovascular effects (QT prolongation, orthostatic hypotension, arrhythmias)","Extrapyramidal symptoms (dystonia, akathisia, tardive dyskinesia)","Neuroleptic malignant syndrome","Serotonin syndrome when combined with other serotonergic drugs","Seizure threshold lowering","Bone marrow suppression (agranulocytosis, leukopenia)","Weight gain and metabolic changes","Angle-closure glaucoma exacerbation","Hepatic impairment","Renal impairment","Avoid abrupt discontinuation"] |
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| Fetal Monitoring | Maternal: Blood pressure, heart rate, ECG at baseline; liver function tests; serum drug levels if toxicity suspected. Fetal: Ultrasound for growth restriction (third trimester); neonatal monitoring for withdrawal symptoms (jitteriness, respiratory distress) for 48 hours postpartum. |
| Fertility Effects | Hyperprolactinemia from perphenazine may cause menstrual irregularities, anovulation, and decreased libido. Amitriptyline may increase prolactin but less pronounced. Both may impair fertility reversibly. |