A sleep supplement widely used to treat insomnia could help reduce reliance on some of the most common and potentially harmful pain medications, new research from the University of Sydney suggests.
Published in PAIN , the study found melatonin can reduce chronic musculoskeletal pain with effects in a similar range to medications such as opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol.
With musculoskeletal pain affecting up to 47 percent of people globally, the findings point to a low-cost, widely available option that could shift how chronic pain is managed.
Melatonin for chronic pain
"Melatonin is already in people's homes, it's inexpensive, and we know it's safe," said lead author and PhD student Kangchao Wu from the Musculoskeletal Research Hub at the Charles Perkins Centre and the School of Health Sciences .
"What's exciting is that melatonin may also help manage chronic pain, opening the door to reducing reliance on medications that come with more risks."
The research highlights the growing potential of drug repurposing – using existing treatments in new ways to deliver faster, more accessible health benefits.
"We're taking a medication we already understand and applying it to a problem that affects a huge proportion of the global population," said co-author Professor Paulo Ferreira , Director of the Musculoskeletal Research Hub.
The study analysed data from 2028 adults across 23 randomised controlled trials conducted in countries including the United States, Russia, Brazil, Egypt and China. Participants included people with conditions such as low back pain, osteoarthritis and fibromyalgia, as well as those recovering from surgeries including joint replacements and spinal procedures.
On average, the study found that melatonin reduced pain by around nine points on a 0-100 scale, with the most rigorous trials showing reductions closer to 10 points, a similar magnitude to widely used pain medications.
The supplement also improved sleep quality, reinforcing the well-established link between pain and sleep.
"For many patients, pain doesn't exist in isolation and is closely tied to poor sleep," Mr Wu said.
"Melatonin appears to target both, which makes it particularly useful for people managing chronic pain."
Across the trials, the dose and timing of melatonin varied depending on the condition and setting. For chronic musculoskeletal pain, doses typically ranged from 3 to 10 mg, with 3 mg per day the most commonly used. For postoperative pain, doses ranged from 1 to 10 mg, with 5 to 6 mg most common. Melatonin was generally taken at bedtime or up to one hour before sleep.
The researchers did not find evidence of a clear dose-response relationship, meaning no single "best" dose can be recommended from the current evidence.
Melatonin safety, side effects and access in Australia
Melatonin is typically low cost – often less than $1.50 per tablet in Australia – and is generally well tolerated, with mild, short-term side effects and no evidence of dependence.
The most commonly reported side effects found in the study were nausea, dizziness and headaches. Overall rates were similar to placebo and no serious adverse events were reported. Melatonin is generally considered safe for short-term use of less than three months.
In Australia, melatonin is not available as a standard over-the-counter supplement. Most products require a prescription, although low-dose melatonin (2 mg or less) can be supplied by a pharmacist without a prescription for short-term treatment of insomnia in adults aged 55 years and older.
Researchers emphasise that patients should discuss melatonin with their doctor before use, especially if they are taking other medicines or have underlying health conditions.
"Our advice isn't for melatonin to replace every pain medication," Mr Wu said. "Instead, after consultation with a doctor, it may be used as an adjunct to existing treatments, particularly for people who also experience sleep problems."
As concerns grow around long-term use of opioids and other pain treatments, the findings highlight a safer alternative that could be integrated into care relatively quicky.
While the researchers say further large-scale studies will strengthen the evidence base, they emphasise the current findings are strong enough to support cautious uptake.
"The level of pain relief we observed is comparable to some conventional treatments, but this does not mean melatonin should replace them," Mr Wu said. "Rather, it may offer a safer additional option within a broader pain management plan."
