SSRI learning module: Principal risks

Very common (> 10%) and common (1–10%) adverse effects:

• Gastrointestinal adverse effects—dry mouth, nausea, vomiting , diarrhoea, constipation
• Central nervous system effects—headache, sleep disturbances, tremor, sedation, lethargy
• Psychiatric effects—agitation and anxiety
• Sexual dysfunction
• Other common adverse effects—sweating, parastesia, joint and muscle pain
• Withdrawal (discontinuation) effects

Rare (0.1–0.01%) and very rare (< 0.01%), but potentially serious adverse effects:

• Serotonin syndrome
• Hypomania/mania or psychosis
• Suicide risk and severe agitation
• Hyponatraemia
• Haemorrhage, particularly gastrointestinal
• Convulsions
• Bone fractures
• Antimuscarinic (anticholinergic) effects—visual disturbances, tachycardia, urinary retention

Important drug interactions:

• Other psychiatric medications—antidepressants (especially serotonergic eg MAOIs), lithium
• 5HT₁ agonists for treating migraine (‘triptans’)
• Antiepileptics
• Antiplatelet medications (aspirin, clopidogrel)
• Linezolid (antibacterial which also has monoamine oxidase inhibiting activity)
• Monoamine oxidase B inhibitors (rasagiline, selegiline)
• Non-steroidal anti-inflammatory drugs
• Oral anticoagulants, including warfarin
• Pimozide
• Tamoxifen—interaction with potent inhibitors of isoenzyme CYP2D6, fluoxetine and paroxetine
• Tramadol

Pregnancy and breast-feeding:

• The decision to prescribe an antidepressant during pregnancy involves very careful assessment of risks to the mother and fetus of untreated depression during the pregnancy and the risks to the fetus of adverse effects including teratogenic effects from exposure to an antidepressant.

Overdose:

• Features of overdose include the usual adverse effects of SSRIs, but very large overdoses can also lead to cardiac features (tachycardia, rhythm disorders, hypotension or hypertension), convulsions, and coma. SSRI overdosage is managed by treating specific symptoms as they arise.