A small, early-stage clinical trial looked at whether adding a high dose of melatonin (300 mg per day) was safe and helpful for people with a specific type of multiple sclerosis (PP-MS) who were already on a stable treatment called ocrelizumab. The study involved only 8 patients, with half receiving melatonin and half receiving a placebo, and planned to follow them for up to two years.
The trial was stopped early. Three out of the four patients who took the high-dose melatonin developed signs of mild liver injury, known as hypertransaminasemia. This liver issue went away after they stopped taking the melatonin. No serious adverse events were reported.
The main reason for caution is that this was a very small study that ended prematurely. The researchers think the liver issue might be due to a possible interaction between the high dose of melatonin and other medications the patients were taking, which are all processed by the liver. This finding does not apply to the much lower doses of melatonin people commonly use for sleep. More research is needed to understand if and how high doses might affect the liver, especially in people taking multiple medications.