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. |
| Molecular Weight | Amitriptyline: 277.4 Da; Perphenazine: 403.97 Da |
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 | Avoid; risk of fetal malformations (e.g., cardiovascular) and teratogenicity associated with amitriptyline, though data limited for perphenazine. Use only if benefit outweighs risk. |
| 2nd trimester | Avoid; potential risks of fetal growth restriction and neurobehavioral effects from amitriptyline. Perphenazine may cause extrapyramidal symptoms in neonate. |
| 3rd trimester | Avoid; risk of neonatal withdrawal (e.g., irritability, respiratory distress) from amitriptyline and extrapyramidal symptoms from perphenazine. Use near term may cause transient neonatal effects. |
Clinical note
CNS depressants may enhance sedative effects Can cause extrapyramidal symptoms and neuroleptic malignant syndrome.
| FDA category | Animal |
| Placental transfer | Both drugs cross the placenta. Amitriptyline and its active metabolite nortriptyline are detectable in cord blood and amniotic fluid. Perphenazine crosses the placenta, though quantitative data are limited. |
■ 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 excipientsConcurrent use with monoamine oxidase inhibitors (MAOIs) or within 14 days of MAOI therapyRecent myocardial infarction (within 6 weeks)Severe hepatic impairmentAngle-closure glaucomaUrinary retention due to prostatic hypertrophy or other causesBone marrow depressionProlonged QT interval or concurrent QT-prolonging drugs (for perphenazine component)Parkinson's disease (for perphenazine component, relative contraindication)
| 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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| Breastfeeding | Both perphenazine and amitriptyline are excreted into breast milk. Amitriptyline levels are low but may accumulate in infants; perphenazine may cause sedation or extrapyramidal effects. Monitor infant for drowsiness, poor feeding, and developmental milestones. Avoid unless essential. |
| Lactation Rating | L4 - Possibly Hazardous |
| 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). |
| 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. |
| Food/Dietary | Avoid excessive alcohol consumption. Grapefruit juice may increase amitriptyline levels; limit intake. High-fiber foods may reduce absorption of amitriptyline; take consistently with respect to meals. Tyramine-rich foods (aged cheese, cured meats, fermented products) are not contraindicated but may cause hypertensive crisis in rare cases; avoid large amounts. |
| Clinical Pearls | 1. Perphenazine is a typical antipsychotic with risk of extrapyramidal symptoms (EPS) and tardive dyskinesia; amitriptyline is a tricyclic antidepressant with anticholinergic and cardiac effects. 2. QT prolongation risk is additive; obtain baseline ECG and monitor electrolytes, especially in elderly or those with cardiac disease. 3. Avoid in patients with narrow-angle glaucoma, urinary retention, or recent MI. 4. Use cautiously with CYP2D6 inhibitors or poor metabolizers; perphenazine and amitriptyline are metabolized by CYP2D6. 5. Abrupt discontinuation may cause withdrawal symptoms; taper gradually. |
| Patient Advice | Take exactly as prescribed; do not stop abruptly due to risk of nausea, headache, or malaise. · This medication may cause drowsiness, dizziness, or blurred vision; avoid driving until you know how it affects you. · Rise slowly from sitting or lying to prevent falls from orthostatic hypotension. · Report any involuntary muscle movements, especially of the face or tongue, as these may indicate tardive dyskinesia. · Avoid alcohol and other CNS depressants (e.g., benzodiazepines, opioids) as they increase sedation and risk of overdose. · Use sun protection; this drug may increase sensitivity to sunlight. · If you have diabetes, monitor blood glucose closely as both components can affect glucose control. |