Duloxetine (Cymbalta): Uses, Dosage, Side Effects, and What to Expect

Duloxetine (brand name: Cymbalta) is a serotonin-norepinephrine reuptake inhibitor (snri). Duloxetine inhibits the reuptake of both serotonin and norepinephrine approximately equally at therapeutic doses, unlike venlafaxine which requires higher doses for significant norepinephrine effects. This balanced dual reuptake inhibition contributes to its efficacy for both mood disorders and pain conditions — descending noradrenergic and serotonergic pathways from the brainstem modulate pain signaling in the spinal cord, explaining why duloxetine helps chronic pain independently of its antidepressant effect.

• Major Depressive Disorder (MDD)
• Generalized Anxiety Disorder (GAD)
• Diabetic Peripheral Neuropathic Pain
• Fibromyalgia
• Chronic Musculoskeletal Pain

Common off-label uses:

• Stress urinary incontinence
• Chemotherapy-induced peripheral neuropathy
• Chronic low back pain
• OCD (limited evidence)

Depression/anxiety: Start 30 mg once daily for 1 week, then increase to 60 mg. Some patients benefit from 120 mg/day. Neuropathic pain/fibromyalgia: 60 mg once daily. Take with food. Avoid in severe hepatic impairment or heavy alcohol use (hepatotoxicity risk).

Some improvement in 1-2 weeks. Full antidepressant effect in 4-6 weeks. Pain effects may take 1-4 weeks.

• Nausea (most common, usually resolves in 1-2 weeks)
• Dry mouth
• Constipation
• Fatigue or drowsiness
• Decreased appetite
• Increased sweating
• Sexual dysfunction
• Dizziness

• Hepatotoxicity (avoid in pre-existing liver disease; avoid heavy alcohol use)
• Serotonin syndrome
• Severe discontinuation syndrome (one of the hardest SNRIs to stop)
• Suicidal ideation in young adults
• Urinary retention
• Orthostatic hypotension
• Hyponatremia

Contraindicated with MAOIs. Strong CYP1A2 inhibitors (fluvoxamine, ciprofloxacin) significantly increase levels. Moderate CYP2D6 inhibitor — can increase levels of drugs metabolized by CYP2D6. Avoid alcohol (hepatotoxicity risk). Caution with NSAIDs and anticoagulants (bleeding risk).

Category C. Third-trimester exposure may cause neonatal discontinuation syndrome. Use only if benefits outweigh risks.

Notorious for severe discontinuation syndrome. Taper very gradually — many patients need 25% reductions every 2-4 weeks. Counting beads from capsules is sometimes used for micro-tapering. Symptoms include brain zaps, dizziness, nausea, irritability, insomnia, and paresthesias.