An old antidepressant, amitriptyline found a second career treating pain
Merck scientists found amitriptyline in the late 1950s, and US regulators approved it in 1961 for depression. Because of its side effects it is rarely a first choice for low mood today, yet it still filled more than 7 million American prescriptions in 2023, much of it for nerve pain, migraine and gut disorders.
Amitriptyline belongs to the tricyclic family of antidepressants and was once sold as Elavil. It does lift depression, but it is more toxic in overdose and harder to tolerate than newer drugs, so guidelines generally keep it as a second-line option. Common side effects include dry mouth, drowsiness, dizziness, constipation and weight gain, while glaucoma, liver damage and heart rhythm problems are rare but serious. Blood levels differ sharply between individuals, and it interacts with many other medicines. It appears on the World Health Organization's list of essential medicines and is sold as a generic.
Its pain record is where it stands out. For painful diabetic nerve damage it works about as well as gabapentin, pregabalin or duloxetine, though it is less well tolerated than the first two. Low doses moderately improve sleep, pain and fatigue in fibromyalgia. In a long-term observational study of 63 people with brainstem strokes, all 16 who developed central pain responded to it, and many relapsed when they stopped.
The evidence has clear limits too. For preventing migraine in adults it is probably effective and roughly matches venlafaxine and topiramate, but in children it performs no better than placebo. The same is true for treatment-resistant depression in adolescents and for depression linked to cancer, though those studies were small, and it does not help nerve pain associated with HIV.
Gut research offers a possible mechanism. In a 2009 study, 74 percent of people with irritable bowel syndrome improved after 12 weeks, and the relief tracked reduced gut sensitivity rather than changes in the nervous system's automatic tone. Researchers suspect the drug calms mast cells near intestinal nerves, easing pain signals directly instead of simply improving mood. A large 2023 trial found it outperformed placebo across several outcomes.
Source: Amitriptyline
