Trimipramine (Surmontil)

What it treats

Trimipramine is approved by the U.S. Food and Drug Administration to treat depression.

Off-label uses include severe primary insomnia and, at times, chronic pain conditions. Off-label means a purpose the label doesn't formally list even though evidence and practice support it.

How it works

Trimipramine acts on serotonin and norepinephrine, two of the brain's chemical messengers. Compared with other tricyclics, its reuptake inhibition is relatively weak. What it does strongly is block histamine and acetylcholine, which is why it's so sedating and so anticholinergic.

The antidepressant effect isn't from the first dose. It comes from slower changes in the brain over the following weeks.

Receptor mechanism (detail)

Trimipramine is a tertiary-amine tricyclic antidepressant. Its reuptake inhibition at SERT and NET is comparatively weak. It's a strong H1 antagonist (hence the deep sedation), a strong muscarinic (M1) antagonist, and an alpha-1 antagonist. It also has meaningful 5-HT2 antagonism. That receptor profile explains the heavy sedation, dry mouth, weight gain, and orthostatic hypotension.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

Starting is 25 to 75 mg at bedtime. Usual range is 75 to 150 mg at bedtime. Higher doses (up to 200 mg per day) are sometimes used in hospital settings. Doses are typically given at bedtime because of the sedation.

Safety monitoring

• ECG at baseline, and periodically at higher doses. Tricyclics prolong QRS, PR, and QTc.
• Overdose is dangerous. Narrow therapeutic index; even modest overdoses can cause fatal arrhythmias.
• Anticholinergic burden. Heavy; Beers Criteria caution in older adults.
• Orthostatic vitals.
• Suicidality in the first 4 weeks, especially under age 25 (FDA boxed warning).
• Serotonin syndrome, avoid MAOIs.
• Reassess at 2, 4, and 6 to 8 weeks.

What to expect

Common side effects

Common side effects include:

• Heavy drowsiness, often into the morning.
• Dry mouth.
• Constipation.
• Blurred vision.
• Weight gain.
• Dizziness on standing.

Several of these come from the anticholinergic and antihistamine effects. If a side effect is severe, or it isn't improving, that's a conversation to have with the prescriber rather than a reason to stop on your own.

Serious side effects and warnings

Serious problems are uncommon, but a few are worth knowing.

Boxed warning. Like all antidepressants, trimipramine carries an FDA boxed warning that it can increase suicidal thoughts and behaviors in children, teenagers, and young adults under 25, especially in the first weeks of treatment or after a dose change.

• Effects on heart rhythm. ECG monitoring matters.
• Danger in overdose. Fatal arrhythmias are possible.
• Anticholinergic burden. Confusion, urinary retention, and falls become real considerations in older adults. Trimipramine is on the Beers list.
• A drop in blood pressure on standing.
• Serotonin syndrome. Do not combine with MAOIs.

Sexual side effects

Trimipramine can reduce sex drive and make orgasm or erection more difficult. Rates are similar to other tricyclics. If sexual side effects appear, they're worth raising with the prescriber.

Weight, appetite, and sleep

Trimipramine commonly increases appetite and causes weight gain. Its strong H1 blockade makes it one of the more sedating tricyclics, which is why it's dosed at bedtime and sometimes chosen when insomnia is a driver.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose is a decision for a prescriber.

Trimipramine comes as capsules. Starting at a low bedtime dose reduces the morning grogginess. A prescriber adjusts the dose based on response and tolerability, often keeping the drug at the low end of the range in outpatient practice.

Missed doses and interactions

If you miss a dose, take it when you remember, unless it's almost time for the next dose. Skip the missed dose and carry on. Don't take two doses to make up for one.

Interactions matter. Trimipramine must not be combined with MAOI antidepressants, and a gap is needed when switching. Alcohol and other sedating medications add to drowsiness. Other anticholinergic medications pile on top of trimipramine's own. Give every prescriber and pharmacist a full list of your medications and supplements, including over-the-counter ones.

Stopping and tapering

Trimipramine isn't a controlled substance and isn't habit-forming in the usual sense.

The body does adjust to it, though, and stopping abruptly can cause discontinuation symptoms: nausea, cholinergic rebound (sweating, GI upset), sleep disturbance, and low mood. A gradual taper planned with a prescriber avoids most of this.

Pregnancy and breastfeeding

This is an area where individual circumstances matter and the decision belongs with a clinician. Untreated depression carries its own risks during pregnancy, and trimipramine passes into breast milk. Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber so the specific risks and benefits can be weighed for their situation.

Cost and generic availability

Trimipramine is available as a generic, though it isn't widely stocked because it isn't commonly prescribed. A pharmacy may need time to source it.

Common questions

Why choose trimipramine? Its heavy sedation and anticholinergic profile occasionally fit depression paired with severe insomnia in a patient who tolerates it. It's not a common first choice today.

How is it different from amitriptyline? Both are strongly sedating and anticholinergic. Trimipramine's reuptake inhibition is weaker; amitriptyline is more balanced. In practice they're similar for tolerability.

Is it dangerous in overdose? Yes. All tricyclics are, and trimipramine is no exception.

Will it cause weight gain? Often, yes. If weight gain becomes a concern, raise it with your prescriber.

Is it addictive? No. It's not a controlled substance and doesn't cause cravings. Stopping should still be done gradually.

Questions to ask your prescriber

• Given how sedating this is, when should I take the dose?
• Which side effects should I expect, and which should I call about?
• Do we need an ECG based on my heart history?
• How long should I plan to take it?
• If we decide to stop it later, how would we do that safely?

Sources

This guide draws on current prescribing information and public health references and current as of June 8, 2026. It is reviewed for clinical accuracy and updated as guidance changes.

• U.S. Food and Drug Administration. Trimipramine maleate (Surmontil) prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Trimipramine.
• National Institute of Mental Health. Mental health medications.
• American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder.
• American Geriatrics Society. Beers Criteria for Potentially Inappropriate Medication Use in Older Adults (2023).