1. Introduction
Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI) used to treat depression, anxiety, and various pain conditions. By increasing serotonin and norepinephrine levels in the central nervous system, duloxetine helps improve mood, reduce anxiety, and alleviate chronic pain, including neuropathic and musculoskeletal pain.
2. Indications
- Approved Indications:
- Major depressive disorder (MDD).
- Generalised anxiety disorder (GAD).
- Diabetic peripheral neuropathic pain.
- Fibromyalgia.
- Chronic musculoskeletal pain (e.g., osteoarthritis, chronic lower back pain).
- Off-Label Uses:
- Stress urinary incontinence.
- Chemotherapy-induced peripheral neuropathy.
3. Dosage
- Adults:
- Major depressive disorder: 40–60 mg daily (can be taken as 20 mg twice daily or 60 mg once daily).
- Generalised anxiety disorder: Start with 30 mg daily, then increase to 60 mg daily. Maximum: 120 mg/day.
- Neuropathic pain, fibromyalgia, or chronic musculoskeletal pain: Start with 30 mg daily, then increase to 60 mg daily.
- Elderly:
- Start at the lowest effective dose (30 mg daily) due to increased sensitivity to side effects.
- Children and Adolescents (≥7 years, for GAD):
- Start with 30 mg daily for 2 weeks, then increase to 60 mg daily if needed.
4. Administration
- Take orally with or without food.
- Swallow capsules whole; do not crush, chew, or open them.
- Consistent timing (e.g., morning or evening) is recommended for optimal therapeutic effect.
5. Forms Available
- Delayed-release capsules: 20 mg, 30 mg, 60 mg.
6. Side Effects
6.1. Common Side Effects
- Nausea.
- Dry mouth.
- Fatigue or drowsiness.
- Dizziness.
- Constipation.
6.2. Less Common Side Effects
- Increased sweating.
- Insomnia.
- Loss of appetite or weight loss.
6.3. Rare but Serious Side Effects
- Hepatotoxicity.
- Suicidal thoughts or behaviour (especially in young adults).
- Serotonin syndrome (e.g., agitation, confusion, rapid heart rate).
- Orthostatic hypotension.
7. Warnings
- Suicidal Thoughts: Increased risk of suicidal ideation in children, adolescents, and young adults during the first few weeks of treatment. Monitor closely.
- Hepatotoxicity: Avoid use in patients with significant alcohol use or pre-existing liver disease due to the risk of liver damage.
- Serotonin Syndrome: Can occur when combined with other serotonergic drugs (e.g., SSRIs, SNRIs, or MAOIs).
- Withdrawal Symptoms: Abrupt discontinuation may cause nausea, dizziness, headache, and irritability. Taper off gradually.
8. Precautions
- Use cautiously in patients with a history of bipolar disorder to avoid triggering mania.
- Monitor for worsening depression or anxiety symptoms during initial therapy.
- Avoid use in patients with uncontrolled narrow-angle glaucoma.
9. Interactions
- Drug-Drug Interactions:
- MAOIs: Contraindicated within 14 days of stopping an MAOI due to risk of serotonin syndrome.
- NSAIDs, aspirin, or anticoagulants: Increased risk of bleeding.
- CYP1A2 inhibitors (e.g., fluvoxamine): May increase duloxetine levels.
- Alcohol: Increases risk of liver damage.
- Drug-Food Interactions:
- No significant food interactions, but taking with food may reduce nausea.
10. Monitoring Parameters
- Monitor for improvement in mood, anxiety, or pain symptoms.
- Watch for side effects such as suicidal ideation, serotonin syndrome, or liver dysfunction.
- Periodic liver function tests in at-risk patients.
11. Use in Children
- Approved for generalised anxiety disorder in children aged 7 years and older. Use with caution, and monitor for behavioural changes and suicidal thoughts.
12. Use in Pregnancy
- Category C: Use only if benefits outweigh the risks. Third-trimester exposure may cause neonatal withdrawal symptoms or respiratory distress.
13. Use in Elderly
- Use cautiously due to increased sensitivity to dizziness, orthostatic hypotension, and liver dysfunction. Start at the lowest effective dose.
14. Use in Kidney Disease
- Avoid in severe renal impairment (creatinine clearance <30 mL/min) due to altered drug clearance.
15. Use in Liver Disease
- Contraindicated in patients with chronic liver disease or substantial alcohol use due to increased risk of hepatotoxicity.
16. Patient Counselling Points
- Take duloxetine as prescribed, and do not stop abruptly without consulting your doctor.
- Report symptoms such as persistent nausea, yellowing of the skin or eyes, or mood changes to your doctor immediately.
- Avoid alcohol to minimise the risk of liver damage.
- It may take 2–4 weeks to feel the full benefits; continue taking it as directed.
- Be cautious with activities requiring alertness (e.g., driving), especially when starting treatment.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Cymbalta | Eli Lilly | $250–300 (30 capsules, 60 mg) |
Irenka | Allergan | $200–250 (30 capsules, 60 mg) |
Generic Duloxetine | Various | $20–50 (30 capsules, 60 mg) |
18. FAQs (15 Questions)
- What is duloxetine used for?
Duloxetine is used to treat depression, anxiety, diabetic neuropathy, fibromyalgia, and chronic musculoskeletal pain. - How does duloxetine work?
It increases serotonin and norepinephrine levels in the brain to improve mood, reduce anxiety, and alleviate pain. - How long does it take for duloxetine to work?
Improvements in mood or pain may take 2–4 weeks, but full effects may take 6–8 weeks. - Can duloxetine cause weight changes?
It may cause mild weight loss due to decreased appetite, but significant changes are uncommon. - What are the common side effects of duloxetine?
Common side effects include nausea, dizziness, dry mouth, and fatigue. - Can I stop duloxetine suddenly?
No, abrupt discontinuation can cause withdrawal symptoms. Taper off gradually under medical supervision. - Is duloxetine safe during pregnancy?
It is not typically recommended but may be used if the benefits outweigh the risks. - Does duloxetine interact with alcohol?
Yes, alcohol increases the risk of liver damage and should be avoided. - What should I do if I miss a dose?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - Can duloxetine be used in children?
Yes, it is approved for generalised anxiety disorder in children aged 7 years and older. - Can duloxetine cause liver damage?
Yes, especially in patients with liver disease or heavy alcohol use. - Does duloxetine interact with other medications?
Yes, it interacts with MAOIs, anticoagulants, and CYP1A2 inhibitors. - Can duloxetine cause insomnia?
It may cause insomnia or drowsiness, depending on the individual. - How should duloxetine be stored?
Store at room temperature, away from moisture and heat. - Is duloxetine addictive?
No, it is not considered addictive but can cause withdrawal symptoms if stopped abruptly.