Serotonin antagonist & reuptake inhibitor (SARI) Pregnancy: §4.6 — Trazodone should only be administered during pregnancy if considered essential by the physician. Data on a limited number (<200) of exposed pregnancies indicate no adverse effects on pregnancy or on the health of the foetus/newborn; safety in human pregnancy has not been established. On basic principles, use during the first trimester should be avoided. When used until delivery, newborns should be monitored for withdrawal symptoms. Breast-feeding: limited data indicate excretion in human breast milk is low, but levels of the active metabolite are not known — weigh benefit of breast-feeding against benefit of therapy.

Trazodone hydrochloride

Brand names: Molipaxin

Trazodone hydrochloride is a sedating antidepressant of the serotonin antagonist and reuptake inhibitor (SARI) class, used for depression, particularly where sleep disturbance or anxiety is prominent.

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: initially 150 mg/day, increased up to 300 mg/day if required

Route: Oral

Frequency: In divided doses after food, or as a single dose on retiring; where divided, the major portion of the dose is taken on retiring

Max: 300 mg/day in usual use; the dose may be further increased to 600 mg/day in divided doses in hospitalised patients

Source: UK SPC (eMC) for Molipaxin 150 mg Tablets, §4.2 (https://www.medicines.org.uk/emc/product/4197/smpc). ANXIETY: 75 mg/day increasing to 300 mg/day as necessary. DEPRESSION ACCOMPANIED BY ANXIETY: as for depression. ELDERLY: for very elderly or frail patients the recommended initial starting dose is reduced to 100 mg/day given in divided doses or as a single night-time dose; this may be incrementally increased, under supervision, according to efficacy and tolerance. In general, single doses above 100 mg should be avoided in these patients, and it is unlikely that 300 mg/day will be exceeded. ADMINISTRATION: a decrease in side-effects (increase of resorption and decrease of peak plasma concentration) can be achieved by taking trazodone after a meal. HEPATIC IMPAIRMENT: trazodone undergoes extensive hepatic metabolism and has been associated with hepatotoxicity — exercise caution when prescribing for patients with hepatic impairment, particularly severe hepatic impairment; periodic monitoring of liver function may be considered. PAEDIATRIC: §4.2 states trazodone 'is not recommended for use in children below the age of 18 years due to a lack of data on safety'; §4.4 adds that suicidal behaviour and hostility have been observed more frequently than with placebo in a clinical study in children and adolescents treated with antidepressants — no paediatric dose is given. Verify any under-18 use against a children's formulary. PRESCRIBING QUANTITY (§4.4): to minimise the potential risk of suicide attempts, particularly at therapy initiation, only restricted quantities should be prescribed at each occasion. The eMC §4.4 was truncated at the source-fetch limit and §4.5 was not retrieved — the interactions listed below come from the US label in this bundle and must be checked against the UK §4.5. US LABELLING DIFFERS on the outpatient ceiling: the US label (A-S Medication Solutions, 2026-07-14) gives a starting dose of 150 mg/day, increases of 50 mg/day every 3 to 4 days, a maximum for outpatients of 400 mg/day and up to 600 mg/day for inpatients.

Dose adjustments

Renal

§4.2 — No dosage adjustment is usually necessary, but caution should be exercised when prescribing for patients with severe renal impairment.

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

Known sensitivity to trazodone or any of the excipients
Alcohol intoxication and intoxication with hypnotics
Acute myocardial infarction

Side effects

Nervous system: serotonin syndrome, convulsion, neuroleptic malignant syndrome, dizziness, vertigo, headache, drowsiness (trazodone is a sedative antidepressant), restlessness, decreased alertness, tremor, blurred vision, memory disturbance, paraesthesia, dystonia
Cardiac: cardiac arrhythmias including Torsade de Pointes, palpitations, premature ventricular contractions, ventricular tachycardia, bradycardia, tachycardia, ECG abnormalities (QT prolongation)
Vascular: orthostatic hypotension, hypertension, syncope
Psychiatric: suicidal ideation or suicidal behaviours, confusional state, insomnia, disorientation, mania, anxiety, nervousness, agitation (very occasionally exacerbating to delirium), delusion, aggressive reaction, hallucinations, nightmares, decreased libido, withdrawal syndrome
Hepato-biliary: abnormal hepatic function (including jaundice and hepatocellular damage), intrahepatic cholestasis, severe hepatic disorders such as hepatitis/fulminant hepatitis and hepatic failure with potentially fatal outcome; elevated liver enzymes
Other: hyponatraemia and SIADH; blood dyscrasias (agranulocytosis, thrombocytopenia, eosinophilia, leucopenia, anaemia); priapism; nausea, vomiting, dry mouth, constipation, diarrhoea (all frequencies 'not known' in §4.8)

Interactions

Monoamine oxidase inhibitors (MAOIs), including linezolid and intravenous methylene blue — increased risk of serotonin syndrome; contraindicated in the US label, which requires at least 14 days between an MAOI and trazodone in either direction (US label §4, §2.4, §7.1)
Other serotonergic drugs — increased risk of serotonin syndrome; monitor, particularly during initiation (US label §7.1)
CNS depressants, including alcohol and barbiturates — trazodone may enhance their effects (US label §7)
Strong CYP3A4 inhibitors — consider reducing the trazodone dose based on tolerability; strong CYP3A4 inducers — consider increasing the dose based on therapeutic response (US label §2.5, §7)
Digoxin or phenytoin — monitor for increased serum levels; warfarin — monitor for increased or decreased prothrombin time (US label §7)
Antiplatelet/anticoagulant drugs (aspirin, NSAIDs, warfarin) — increased risk of bleeding (US label §5.5). NOTE: the UK SPC §4.5 was not retrieved in this bundle.

Clinical monograph

How it works

It inhibits serotonin reuptake and antagonises 5-HT2A receptors, with additional alpha-1-adrenergic and histamine H1 blockade that accounts for its marked sedative effect.

Prescribing in practice

Warn patients about the rare but urgent risk of priapism, which requires immediate medical attention to avoid permanent injury.
Postural hypotension and sedation are common, so dose is usually taken at night and titrated cautiously in older or frail patients.
Avoid combining with other serotonergic agents and monoamine oxidase inhibitors because of serotonin syndrome and QT-prolongation risk.

Monitoring

Monitor mood, suicidal ideation (especially early and after dose changes), blood pressure and, where cardiac risk exists, the QT interval.

Counselling the patient

Take the main dose at bedtime as it causes drowsiness, and do not drive until you know how it affects you.
Seek urgent care for a prolonged or painful erection.
Do not stop suddenly; the dose should be reduced gradually under guidance.

Evidence & guidelines

Antidepressant prescribing and the standard suicidality warning for under-25s are governed by NICE depression guidance and MHRA advice.

Reference: NICE NG222/NG97; 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