TRIMIPRAMINE MALEATE
Clinical safety rating: caution
Animal studies have proved adverse effects but may be safe for humans
Inhibits reuptake of norepinephrine and serotonin, with moderate anticholinergic, sedative, and antihistaminergic effects.
| Metabolism | Hepatic via CYP450 (CYP2D6, CYP2C19, CYP3A4) to active metabolite desmethyltrimipramine; also glucuronidation. |
| Excretion | Renal: ~70% as metabolites (unchanged <5%); fecal: ~30% via biliary excretion. |
| Half-life | Terminal elimination half-life: 22–32 hours (mean 24 hours); in elderly or hepatic impairment, may extend to 40–50 hours requiring dose adjustment. |
| Protein binding | 94–96% bound primarily to alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | 17–30 L/kg (mean 25 L/kg), indicating extensive tissue binding and distribution beyond plasma volume. |
| Bioavailability | Oral: 35–60% due to first-pass metabolism; intramuscular: 70–90% (not commercially available in all regions). |
| Onset of Action | Oral: Antidepressant effect 2–3 weeks; sedative effect within 1–2 hours. IV (not typical for depression): within 30 minutes for sedative effect. |
| Duration of Action | Oral: Antidepressant effect sustained for 24 hours with once-daily dosing; sedative effect persists 6–8 hours after a single dose. Steady-state achieved in 5–10 days. |
| Molecular Weight | 410.51 Da (trimipramine maleate salt) |
25-150 mg orally once daily at bedtime, starting at 25 mg and titrating up by 25 mg every 3-4 days.
| Dosage form | CAPSULE |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment. For severe renal impairment (eGFR <30 mL/min), use with caution; consider reducing dose by 50% or increasing dosing interval. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Start at 50% of normal dose and titrate slowly. Child-Pugh Class C: Contraindicated. |
| Pediatric use | For adolescents (12-18 years) with depression: 25-50 mg orally once daily at bedtime, starting at 25 mg and titrating up by 25 mg every 5-7 days. Not recommended in children under 12. |
| Geriatric use | Start at 10-25 mg orally once daily at bedtime, increase by 10 mg every 5-7 days to a maximum of 100 mg/day. Caution with concurrent medications due to anticholinergic effects. |
| 1st trimester | Avoid due to risk of neural tube defects and other congenital malformations. Use only if benefit outweighs risk. Consider alternative therapy. |
| 2nd trimester | Avoid unless essential. May cause fetal tachycardia or withdrawal symptoms. Monitor fetal growth and cardiac function. |
| 3rd trimester | Avoid near term. Risk of neonatal withdrawal symptoms (irritability, tremor, respiratory distress) and anticholinergic effects (ileus, urinary retention). |
Clinical note
MAOIs can cause serotonin syndrome and hyperpyrexia Strong anticholinergic effects may occur with other drugs Increased risk of suicide in children and young adults.
| Placental transfer | Crosses placenta. Fetal plasma concentrations approximately 50-80% of maternal levels. Active transport via P-glycoprotein may limit exposure. |
| Breastfeeding | Trimipramine is excreted into breast milk in small amounts (relative infant dose 0.5-2%). Monitor infant for drowsiness, poor feeding, and weight gain. Use with caution; consider alternative antidepressants with better safety profile (e.g., sertraline). |
■ FDA Black Box Warning
Suicidal thoughts and behaviors in children, adolescents, and young adults; not approved for pediatric use except for nocturnal enuresis.
| Common Effects | Dry mouth |
| Serious Effects |
Hypersensitivity to trimipramine or any componentConcomitant use with MAOIs (risk of serotonin syndrome)Recent myocardial infarction (within 6 weeks)Severe hepatic impairmentNarrow-angle glaucomaUrinary retention (due to anticholinergic effects)Breastfeeding (relative; see breastfeeding notes)
| Precautions | Serotonin syndrome, anticholinergic effects (e.g., urinary retention, constipation, blurred vision), cardiovascular effects (QT prolongation, orthostatic hypotension), seizures, mania/hypomania, angle-closure glaucoma, bone marrow suppression, hepatic impairment, withdrawal syndrome. |
| Food/Dietary |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Trimipramine is a tricyclic antidepressant (TCA) with limited human data. First trimester: observational studies suggest a small increased risk of congenital malformations, particularly cardiovascular defects (RR ~1.2-1.5). Second/third trimester: risk of neonatal withdrawal syndrome (irritability, tachycardia, respiratory distress) and anticholinergic effects (constipation, urinary retention). No specific syndrome reported. |
| Fetal Monitoring | Maternal: blood pressure, heart rate, ECG (baseline and periodic due to QT prolongation risk), serum drug levels (if toxicity suspected), mood symptoms, seizure threshold. Fetal: fetal growth ultrasound, fetal heart rate monitoring in late pregnancy for signs of distress or withdrawal. |
| Fertility Effects | Trimipramine may cause hyperprolactinemia via dopamine D2 receptor blockade, leading to galactorrhea, amenorrhea, and potential ovulation disruption. Reversible upon discontinuation. No direct gonadal toxicity reported. |
| Avoid alcohol. Limit caffeine intake as it may exacerbate side effects. No specific food restrictions; but take with food if GI upset occurs. |
| Clinical Pearls | Trimipramine has significant sedative properties; it is often used for insomnia in depression. It has a lower incidence of anticholinergic side effects compared to other TCAs. Monitor for QTc prolongation, especially in elderly or those with cardiac disease. Do not discontinue abruptly; taper to avoid withdrawal symptoms. |
| Patient Advice | Take at bedtime due to drowsiness. · Avoid alcohol and other CNS depressants. · May take 2-4 weeks to see full benefit; do not stop abruptly. · Report any signs of suicidal thoughts or worsening depression. · Avoid driving until you know how the drug affects you. · Notify your doctor if you experience urinary retention, blurred vision, or constipation. |