From the Guidelines
The half-life of melatonin is approximately 40 to 60 minutes in healthy adults. This information is crucial for understanding how melatonin levels fluctuate throughout the day and night, as discussed in the context of circadian rhythm biomarkers 1. Melatonin levels are typically very low during the day but begin to rise 1–3 h before habitual sleep onset time, remain elevated during the night, and return to low daytime levels usually within 1 h of habitual wake time 1. Some key points to consider about melatonin include:
- Melatonin production is predominantly controlled by the suprachiasmatic nucleus (SCN) and is a key biomarker of the central circadian clock 1.
- Factors such as light exposure, postural changes, exercise, and certain substances (like NSAIDs, beta-blockers, and alcohol) can affect melatonin levels 1.
- A washout period without certain substances and careful sampling conditions are necessary for accurate assessment of melatonin levels 1. Given the short half-life of melatonin, its supplementation is often recommended 30-60 minutes before desired sleep time to help with sleep onset difficulties. However, for sleep maintenance issues, extended-release formulations may be more beneficial due to their slower release of melatonin over several hours. It's also important to note that individual factors such as age, liver function, and certain medications can influence melatonin metabolism and its half-life 1.
From the Research
Melatonin Half-Life
- The half-life of melatonin is approximately 0.95 hours for immediate-release melatonin 2 and 1.63 hours for extended-release melatonin 2.
- A study comparing the pharmacokinetics of extended-release melatonin to immediate-release melatonin found that extended-release melatonin had a longer elimination half-life and time to peak concentration 2.
- The pharmacokinetic profile of extended-release melatonin suggests that it could be used for future efficacy studies of melatonin and sleep outcomes 2.
Factors Affecting Melatonin Half-Life
- The formulation of melatonin, either immediate-release or extended-release, can affect its half-life 2.
- Age may also be a factor, as one study found that prolonged release melatonin was efficacious in patients with a mean age of 55 or older 3.
Comparison to Ramelteon
- Ramelteon, a melatonin receptor agonist, has been studied for the treatment of insomnia and has shown efficacy in reducing sleep latency and improving sleep quality 4, 5, 3.
- The half-life of ramelteon is not explicitly stated in the provided studies, but its pharmacokinetic properties are distinct from those of melatonin 4, 5.