Does Duloxetine Cause Myalgia?
Duloxetine does not cause myalgia (muscle pain) as a recognized adverse effect; in fact, it is used to treat muscle pain in conditions like fibromyalgia and chronic musculoskeletal pain. The FDA-approved prescribing information does not list myalgia as an adverse reaction, and the drug is specifically indicated for managing pain conditions 1.
Evidence from FDA Drug Labeling
The comprehensive FDA adverse reaction profile for duloxetine, based on over 8,000 patients across multiple placebo-controlled trials, does not include myalgia among reported adverse effects 1. The most common adverse reactions (occurring in ≥5% of patients and at least twice the rate of placebo) were:
- Nausea
- Dry mouth
- Somnolence
- Constipation
- Decreased appetite
- Hyperhidrosis (excessive sweating) 1
Notably absent from this extensive safety database is any mention of muscle pain or myalgia as a treatment-emergent adverse reaction 1.
Therapeutic Use for Muscle Pain
Duloxetine is FDA-approved and guideline-recommended specifically for treating painful musculoskeletal conditions 2:
- Fibromyalgia: Duloxetine 60 mg daily reduces pain with a number needed to treat (NNT) of 8, demonstrating efficacy in treating widespread muscle pain 3, 4
- Chronic low back pain: Shows small short-term improvements in pain intensity 2
- Osteoarthritis pain: Associated with small improvements in pain severity and function 2
Mechanism of Action
Duloxetine works by enhancing the endogenous descending pain inhibition system through dual serotonin and norepinephrine reuptake inhibition 5. Over 90% of its pain-relieving effect is due to direct analgesic action rather than indirect antidepressant effects 5.
Common Pitfalls to Avoid
Do not confuse pre-existing muscle pain with drug-induced myalgia. Patients prescribed duloxetine typically have chronic pain conditions; any muscle pain they experience is far more likely related to their underlying condition than to the medication itself 6.
If a patient reports new or worsening muscle pain after starting duloxetine, consider: