Melatonin Nasal Spray

Melatonin as a research molecule

Melatonin is synthesised from serotonin in the pineal gland through N-acetylation and O-methylation, and its release follows a pronounced light-entrained daily rhythm. Because that rhythm is so reliable, melatonin secretion profiles are used as a readout of circadian phase in chronobiology research, and exogenous melatonin is used as a phase-shifting probe in the same models.

Receptor pharmacology

• MT1 and MT2 are G-protein-coupled receptors expressed in the suprachiasmatic nucleus and in peripheral tissues.
• MT1 and MT2 signalling has been dissected using selective agonists and antagonists, with the two subtypes associated with different aspects of circadian and sleep-related physiology in animal models.
• Melatonin also has direct antioxidant chemistry independent of receptor binding, which is studied separately in oxidative-stress models.

Why the intranasal route is investigated

Orally administered melatonin undergoes extensive hepatic first-pass metabolism, mainly 6-hydroxylation by CYP1A enzymes, and reported bioavailability varies widely between individuals. Nasal delivery avoids that first pass, and pharmacokinetic comparisons in animal models have examined how quickly plasma concentrations rise and how reproducible the exposure is relative to oral dosing. A separate strand of the literature examines nose-to-brain transport along olfactory and trigeminal pathways, a mechanism that remains debated and is an active methodological question rather than a settled finding.

Formulation variables

For a spray, the formulation is part of the experiment. Melatonin's limited aqueous solubility means co-solvents or solubilising excipients are generally required, and those excipients can influence mucosal residence time and absorption in their own right. Droplet size distribution, spray plume geometry and pump actuation volume are standard characterisation endpoints in intranasal delivery research, alongside content assay and photostability testing.

Store the bottle refrigerated at 2–8 °C, upright and protected from light, and do not freeze it — freezing can crack the bottle and disturb the pump seal. Melatonin in aqueous solution photodegrades, so keep it in its original light-protected container and limit bench-top exposure. Prime the pump according to the label before recording any actuation volume, and discard the first actuations from a new bottle rather than counting them as data. Wipe the nozzle after use, record the lot number and concentration with your results, and dispose of unused solution as laboratory chemical waste.