Duloxetine Side Effects
Duloxetine commonly causes nausea, dry mouth, sleepiness, fatigue, constipation, loss of appetite, increased sweating, and dizziness, with nausea being the most frequent reason patients stop the medication. 1
Most Common Side Effects
The FDA-approved labeling identifies these as the most frequently occurring adverse effects 1:
- Nausea (most common reason for discontinuation)
- Dry mouth
- Sleepiness/somnolence
- Fatigue
- Constipation
- Loss of appetite
- Increased sweating (hyperhidrosis)
- Dizziness
Duloxetine has slightly higher discontinuation rates due to adverse effects compared to SSRIs as a class (67% increased risk versus SSRIs), with nausea and vomiting being particularly problematic 2.
Serious Adverse Effects Requiring Monitoring
1. Liver Damage
Watch for itching, right upper abdominal pain, dark urine, jaundice, or elevated liver enzymes. Avoid duloxetine in patients with hepatic disease 1.
2. Blood Pressure Changes and Falls
- Can increase blood pressure during treatment
- Can cause orthostatic hypotension with dizziness/fainting, especially when starting or increasing dose
- Increased fall risk, particularly in elderly patients
- Monitor blood pressure before starting and throughout treatment 1
3. Serotonin Syndrome (Life-Threatening)
Symptoms include agitation, hallucinations, coordination problems, muscle twitching, racing heartbeat, fever, nausea/vomiting, muscle rigidity, tremor, and seizures. Risk increases when combined with other serotonergic medications (triptans, SSRIs, SNRIs, MAOIs, tramadol, fentanyl, St. John's Wort) 1.
4. Abnormal Bleeding
Increased risk of bleeding or bruising, especially when combined with warfarin, NSAIDs, or aspirin 1.
5. Discontinuation Syndrome
Do not stop duloxetine abruptly. Rapid discontinuation causes anxiety, irritability, fatigue, sleep problems, headache, sweating, dizziness, electric shock-like sensations, vomiting, nausea, and diarrhea 1. Recent data shows drug withdrawal syndrome is one of the highest reported adverse events, with cases peaking in 2017 3.
6. Hyponatremia
Low sodium levels, particularly in elderly patients. Symptoms include headache, weakness, unsteadiness, confusion, and memory problems 1. This has been documented even in pediatric patients 4.
7. Urinary Retention
Decreased urine flow or inability to pass urine 1.
8. Manic Episodes
Increased energy, severe insomnia, racing thoughts, reckless behavior, excessive happiness or irritability 1.
9. Visual Problems
Eye pain, vision changes, swelling or redness around the eye. Consider eye examination for at-risk patients 1.
10. Seizures
Risk of convulsions, particularly upon treatment discontinuation 1.
Special Population Considerations
Pediatric Patients (7-17 years)
Most common side effects include nausea, decreased weight, and dizziness. Monitor height and weight regularly as duloxetine causes mean weight decrease of 0.1 kg at 10 weeks (versus 0.9 kg gain with placebo), with 16% experiencing clinically significant weight loss 1.
Pregnancy and Breastfeeding
Duloxetine passes into breast milk. Depression during pregnancy is associated with premature birth, but antidepressant use has not been shown to improve these outcomes and may increase preterm delivery risk 2, 1.
Rare but Notable Adverse Effects
Recent postmarketing surveillance identified additional concerns 1, 3:
- Reproductive system and breast disorders (not mentioned in original labeling)
- Acid reflux (reported in 1.38% of patients) 5
- Acute pancreatitis
- Anaphylactic reaction
- Angle-closure glaucoma
- Hypertensive crisis
- Hallucinations
- Aggression and anger (particularly early in treatment)
Clinical Pitfalls to Avoid
- Do not combine with heavy alcohol use - associated with severe liver injury 1
- Avoid in severe renal impairment or hepatic disease 6
- Do not use with thioridazine - can cause serious heart rhythm problems or sudden death 1
- Doses above 60 mg/day are not more effective and cause more side effects 6
- Taper gradually when discontinuing - use a two-week taper schedule to minimize withdrawal syndrome 7