PAMELOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PAMELOR (PAMELOR).
Nortriptyline, the active ingredient, is a tricyclic antidepressant that inhibits the reuptake of norepinephrine and serotonin at the presynaptic neuronal membrane, increasing their availability in the synaptic cleft.
| Metabolism | Primarily hepatic via CYP2D6 and CYP3A4; also undergoes glucuronidation. Active metabolite: 10-hydroxynortriptyline. |
| Excretion | Primarily renal (approximately 70% as metabolites, 40-50% as glucuronide conjugates, 20-30% as free or conjugated nortriptyline; <5% unchanged), with 20-30% biliary/fecal elimination. |
| Half-life | Mean terminal elimination half-life is 18-24 hours (range 13-40 hours) in adults; prolonged in elderly and hepatic impairment (up to 60 hours). Steady-state achieved in 4-5 days. |
| Protein binding | 93-95% bound, primarily to alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | Approximately 15-25 L/kg, indicating extensive tissue distribution and high lipophilicity. |
| Bioavailability | Oral: 40-60% (due to extensive first-pass metabolism). |
| Onset of Action | Oral: 2-4 weeks for antidepressant effect; rapid onset of sedation within 1-2 hours. IM (not typical): 1-2 hours for sedation. |
| Duration of Action | Antidepressant effect: sustained with chronic dosing; sedation lasts 6-8 hours after a single dose. Analgesic effect in neuropathic pain: 12-24 hours. |
| Molecular Weight | 263.38 |
25-150 mg orally per day, typically as a single daily dose at bedtime or in divided doses; start at 25 mg 1-3 times daily and titrate gradually. Maximum 150 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | GFR 30-59 mL/min: reduce dose by 25-50%; GFR 15-29 mL/min: reduce dose by 50% and use with caution; GFR <15 mL/min: avoid use (limited data; risk of accumulation). |
| Liver impairment | Child-Pugh A: caution, consider 50% dose reduction; Child-Pugh B: reduce dose by 50-75% and monitor closely; Child-Pugh C: contraindicated. |
| Pediatric use | Not approved for children <12 years; for adolescent depression: 1-3 mg/kg/day orally in divided doses, max 100 mg/day. |
| Geriatric use | Start at 10-25 mg/day orally, increase by 10-25 mg every 3-7 days as tolerated; usual range 25-75 mg/day; monitor for anticholinergic effects, sedation, orthostatic hypotension. |
| 1st trimester | Avoid. Risk of congenital malformations, particularly cardiac defects, based on some studies. Use only if benefits outweigh risks. |
| 2nd trimester | Use with caution. Associated with increased risk of preterm birth and low birth weight. Limited safety data. |
| 3rd trimester | Avoid near term. Risk of neonatal withdrawal syndrome (irritability, hypertonia, tremors) and persistent pulmonary hypertension of the newborn (PPHN). |
Clinical note
Comprehensive clinical and safety monograph for PAMELOR (PAMELOR).
| Placental transfer | Crosses placenta; fetal serum concentrations can be 30-50% of maternal levels. Evidence of transfer via umbilical cord blood. |
| Breastfeeding | Nortriptyline is excreted into breast milk in low concentrations. The American Academy of Pediatrics considers it compatible with breastfeeding, but monitor infant for drowsiness and poor feeding. Lowest effective dose recommended. |
■ FDA Black Box Warning
WARNING: Suicidality and Antidepressant Drugs. Antidepressants increased the risk of suicidal thinking and behavior in short-term studies in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders. Monitor closely for worsening and emergence of suicidal thoughts and behaviors.
| Serious Effects |
Hypersensitivity to nortriptyline or any tricyclic antidepressantRecent myocardial infarctionConcurrent use of MAOIs (risk of serotonin syndrome; allow 14 days washout)Use of linezolid or intravenous methylene blue
| Precautions | Risk of suicidality, Activation of mania/hypomania, QT prolongation and cardiac arrhythmias, Orthostatic hypotension, Serotonin syndrome, Angle-closure glaucoma, Urinary retention, Seizure threshold lowering, Bone marrow suppression (agranulocytosis), Anticholinergic effects, Discontinuation syndrome |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they may increase nortriptyline levels. Consuming large amounts of caffeine or tyramine-rich foods (e.g., aged cheeses, cured meats) may theoretically increase risk of hypertensive crisis, though less common with TCAs. Alcohol should be avoided due to additive CNS depression. |
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| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Pamelor (nortriptyline) is a tricyclic antidepressant. First trimester: Limited human data show no consistent association with major malformations; however, animal studies have shown adverse effects at high doses. Second and third trimesters: Use may be associated with transient neonatal withdrawal symptoms (irritability, tachycardia, respiratory distress) and anticholinergic effects. Risk may be dose-dependent. |
| Fetal Monitoring | Monitor maternal mood and side effects (anticholinergic, cardiac). Fetal monitoring: serial ultrasounds for growth and amniotic fluid volume if third-trimester exposure. Neonatal monitoring after delivery for withdrawal symptoms (irritability, abnormal tone, respiratory distress) for at least 48 hours. |
| Fertility Effects | Limited data. Tricyclic antidepressants may cause sexual dysfunction (libido, ejaculation) potentially affecting fertility in males. In females, no established impact on ovulation or conception risk. |
| Clinical Pearls | Pamelor (nortriptyline) is a secondary amine tricyclic antidepressant with fewer anticholinergic and sedative effects than tertiary amines. Monitor plasma levels (therapeutic range 50–150 ng/mL) to avoid toxicity. Use with caution in patients with cardiovascular disease due to risk of QT prolongation and arrhythmias. Avoid abrupt discontinuation to prevent withdrawal symptoms. Therapeutic onset may take 2–4 weeks. |
| Patient Advice | Take exactly as prescribed; do not change dose or stop without consulting your doctor. · It may take several weeks to feel the full benefit; do not stop if you do not see immediate improvement. · Avoid alcohol and other CNS depressants as they can increase side effects like drowsiness and dizziness. · Rise slowly from sitting or lying positions to prevent dizziness or fainting. · Notify your doctor immediately if you experience rapid heartbeat, chest pain, or mood changes like worsening depression or suicidal thoughts. · May cause dry mouth; use sugarless candy or ice chips for relief. · Avoid driving or operating heavy machinery until you know how this medication affects you. · Keep out of reach of children; overdose can be fatal. |