SSRI, SNRI and other antidepressant adverse effects — Rapid

Synopsis

Identify antidepressant adverse effects early, separate tolerable adjustment symptoms from time-critical toxicity, and adapt prescribing without overlooking depression, withdrawal, interactions or the person's treatment priorities.

Ask about nausea, bowel change, sleep, sweating, sexual function and agitation before attributing poor adherence to lack of motivation.
SSRIs can impair platelet aggregation; NSAIDs, antiplatelets and anticoagulants increase the clinical importance of gastrointestinal bleeding risk.
Citalopram and escitalopram have dose-related QT risk; contraindicated combinations and electrolyte abnormalities must be checked explicitly.
Venlafaxine can raise blood pressure and produces troublesome withdrawal when doses are missed; check pressure before treatment and after increases.
Mirtazapine often increases appetite and sedation, whereas tricyclic medicines add anticholinergic, postural and overdose hazards.
Agomelatine requires baseline and scheduled liver testing, including renewed testing after dose escalation.
Review after one week when starting an antidepressant in people aged 18–25 or when suicide risk is a particular concern; otherwise the first review is usually within two weeks.

Key red flags

New agitation with inducible or spontaneous clonus, hyperreflexia and autonomic disturbance after a serotonergic addition requires urgent assessment for serotonin syndrome.

Confusion, falls or seizure after initiation, particularly with a thiazide or in an older adult, warrants urgent sodium measurement.

Jaundice, dark urine or sustained unexplained fatigue during agomelatine treatment requires immediate cessation and liver assessment.

Investigation priorities

Medication reconciliationFirst step

Identify pharmacological contributors and the chronology of new symptoms.

Management branches

TolerabilityManage non-urgent adverse effects

Symptoms are troublesome but there are no physiological or psychiatric emergency features.

Check onset, severity, benefit so far and the patient's priorities before changing the prescription.
Discuss a practical timing adjustment, slower titration or dose review appropriate to the actual medicine.
Agree when to reassess and consider a planned switch if the burden persists despite an adequate management attempt.

Key medicines

Sertraline for adult depressionA licensed starting regimen is 50 mg orally once daily; if needed increase by 50 mg at intervals of at least one week, to a maximum 200 mg daily.Use lower or less frequent dosing in hepatic impairment; avoid severe hepatic impairment, contraindicated MAOI combinations and unexamined serotonergic interactions.

Agomelatine for major depressionGive 25 mg orally at bedtime; after two weeks consider 50 mg nightly if symptoms have not improved and the benefit-risk assessment supports escalation.Contraindicated in hepatic impairment and with potent CYP1A2 inhibitors such as fluvoxamine or ciprofloxacin; do not use at age 75 or over.

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