Tricyclic antidepressant (sedating) Pregnancy: §4.6 — Do not use in pregnancy, especially during the first and last trimesters, unless there are compelling reasons; there is no evidence from animal work that it is free from hazard. Trimipramine is contraindicated during lactation. §4.8 records withdrawal symptoms, respiratory depression and agitation in neonates whose mothers had taken trimipramine during the last trimester.

Trimipramine

Brand names: Surmontil

Trimipramine is a tricyclic antidepressant used in the treatment of depression, particularly where sedation is desirable.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Depression: 50-75 mg/day initially, increasing to 150-300 mg/day; maintenance dose 75-150 mg/day

Route: Oral

Frequency: In divided doses or as one dose at night

Source: UK SPC (eMC) for Trimipramine 10 mg Tablets, §4.2 (https://www.medicines.org.uk/emc/product/2961/smpc). ELDERLY: 10-25 mg three times a day initially; the initial dose should be increased with caution under close supervision, and half the normal maintenance dose may be sufficient to produce a satisfactory clinical response. PAEDIATRIC: §4.2 states 'Children: Not recommended' — no paediatric dose is given. Verify any under-18 use against a children's formulary. No absolute adult maximum daily dose is stated in the retrieved eMC §4.2 (the stated range rises to 300 mg/day). WITHDRAWAL (§4.8): withdrawal symptoms may occur on abrupt cessation and include insomnia, irritability and excessive perspiration. MONITORING (§4.4): patients with an established diagnosis of diabetes mellitus or with risk factors for diabetes should have appropriate glycaemic monitoring; trimipramine may dose-dependently prolong the QT interval; concomitant buprenorphine/opioids may result in serotonin syndrome. The eMC §4.4 was truncated at the source-fetch limit and §4.5 was not retrieved — the interactions below are drawn from the §4.4 text and from the US label in this bundle. US LABELLING DIFFERS (Bryant Ranch Prepack, 2023-06-14): outpatients initially 75 mg/day in divided doses increased to 150 mg/day with dosages over 200 mg/day not recommended and maintenance 50-150 mg/day; hospitalised patients initially 100 mg/day increased gradually to 200 mg/day and, if no improvement in 2 to 3 weeks, to a maximum recommended dose of 250 to 300 mg/day; adolescent and geriatric patients initially 50 mg/day with gradual increments up to 100 mg/day. CLINICIAN CHECK: the US label's Drug Interactions section in this bundle contains an apparently misplaced dosing sentence — 'In resistant cases of depression in adults, a dose of 2.5 mg/kg/day may have to be exceeded. If a higher dose is needed, ECG monitoring should be maintained during the initiation of therapy and at appropriate intervals during stabilization of dose'. It is stated for ADULTS, is not a paediatric regimen, and has deliberately NOT been used as a dose here.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Recent myocardial infarction
Any degree of heart block or other cardiac arrhythmias
Mania
Severe liver disease
During breast feeding
Hypersensitivity to trimipramine maleate or to any of the excipients

Side effects

Anticholinergic (common early in treatment, usually lessening): dry mouth, disturbance of accommodation, tachycardia, constipation, hesitancy of micturition
Common: drowsiness, sweating, postural hypotension, tremor, skin rashes; interference with sexual function may occur
Cardiac: arrhythmias and severe hypotension are likely with high dosage or in deliberate overdose, and may occur at normal dosage in pre-existing heart disease; QT interval prolongation and torsade de pointes
Rare but serious: bone marrow depression including agranulocytosis, cholestatic jaundice, hypomania, convulsions, peripheral neuropathy
Psychiatric: suicidal ideation and suicidal behaviours reported during therapy or early after discontinuation; psychotic manifestations including mania and paranoid delusions may be exacerbated
Metabolic/other: hyperglycaemia and an increased risk of diabetes mellitus in depressed patients receiving tricyclics; increased risk of bone fractures (mainly in patients 50 years and older)

Interactions

Buprenorphine/opioids and other serotonergic agents — may result in serotonin syndrome, a potentially life-threatening condition; careful observation is advised, particularly during initiation and dose increases (§4.4)
MAOIs, including linezolid and intravenous methylene blue — contraindicated in the US label because of the risk of serotonin syndrome; at least 14 days should elapse in either direction between an MAOI and trimipramine (US label, Contraindications and Dosage and Administration)
Cimetidine — inhibits elimination of tricyclic antidepressants; downward adjustment of trimipramine dosage may be required if cimetidine is started, and upward adjustment if it is stopped (US label)
Alcohol — concomitant use may be associated with exaggerated effects (US label)
Sympathomimetic amines, local decongestants, local anaesthetics containing epinephrine, atropine or drugs with an anticholinergic effect — tricyclic antidepressants can potentiate the effects of catecholamines and atropine-like effects may be more pronounced (US label)
CYP2D6 substrates/poor metabolisers — the US label flags reduced CYP2D6 activity in about 7-10% of caucasians (text truncated at the source-fetch limit). NOTE: the UK SPC §4.5 was not retrieved in this bundle.

Clinical monograph

How it works

It inhibits reuptake of noradrenaline and serotonin and has marked antagonism at histamine H1, muscarinic and alpha-adrenergic receptors, accounting for its sedative and antimuscarinic profile.

Prescribing in practice

Tricyclic antidepressants are dangerous in overdose, causing cardiac arrhythmias, seizures and coma, so the risk should be assessed in patients at risk of self-harm.
Antimuscarinic effects and postural hypotension are common, warranting caution in cardiac disease, glaucoma, prostatic hypertrophy and the elderly.
It lowers the seizure threshold and should be used with caution in epilepsy, avoiding abrupt withdrawal.

Monitoring

Monitor mood and suicidal ideation, cardiovascular status and antimuscarinic side effects, particularly when initiating or adjusting treatment.

Counselling the patient

This medicine is sedating and may cause drowsiness; avoid driving until you know how it affects you.
Dry mouth, blurred vision and constipation are common, especially at first.
It can be very dangerous in overdose, so take only as prescribed and seek advice before stopping.

Evidence & guidelines

The overdose toxicity of tricyclic antidepressants such as trimipramine is well documented and reflected in NICE depression guidance.

Reference: NICE NG222; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways