CHRONOPHARMACOLOGY OF MELATONIN IN A GROU P OF NORMAL SUBJECTS IN MEXICO-CITY

The possible use of melatonin (MEL) as a therapeutic agent in psichiat ry has been studied for many years, especially in sleep disorders. How ever, information regarding the optimum time and the best administrati on route for this hormone is scarce and confuse. The present study rep orts the pharmacokinetics of MEL in a group of nine healthy volunteers that recieved a single total dose of 20 mg either in the morning (08: 00 h) or al night (20:00 h). Results demonstrate significat difference s depending on the time of administration. When administered fn the mo rning, MEL plasmatic levels were higher and attained its maximum conce ntrations in a shorter time. These results indicate that independently of the administered dose, the biodisponibility of MEL is significantl y influenced by the circadian temporal organization of the organism.