Abstract
Melatonin is a molecule that is essentially secreted by the pineal gland. The oral bioavailability of immediate release melatonin is low, and several pharmacokinetic parameters have a high variability in C max and volume of distribution. The aim of this study was to investigate the bioavailability pro fi le of long acting melatonin in Mexicans. Twelve healthy volunteers participated into the study. After 12 hour overnight fast, subjects received a single capsule of long acting of melatonin 5 mg dose. For the pharmacokinetic analysis, blood samples were drawn at baseline, 0.25, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 3.0, 4.0, 6.0, 8.0, 10.0, 12.0 and 24.0 hours after dosing. The pharmacokinetic values were C max of 8.768 ± 7.043 ng/mL, T max of 2.7 ± 0.77 h, AUC 0-t of 29.814 ± 24.931 h.ng/ mL, AUC 0- ∞ of 38.537 ± 24.658 h.ng/mL, Cl of 185.293 ± 121.806 L/h, Vd of 451.370 ± 510.039 L and t ½ of 1.509 ± 0.768 h. The pharmacokinetic values of long acting melatonin of our study showed a high variability in C max , clearance, half- life time and apparent volume of distribution in Mexican volunteers, and there are consistent with the great variability reported in other populations that used the short acting melatonin.
Highlights
Melatonin (N-acetyl-5-methoxytryptamine) is a small lipophile molecule that is essentially secreted by the pineal gland and its synthesis shows a circadian pattern (Weaver et al, 1993; Jung and Ahmad, 2006)
The pharmacokinetic values of long acting melatonin of our study showed a high variability in Cmax, clearance, halflife time and apparent volume of distribution in Mexican volunteers, and there are consistent with the great variability reported in other populations that used the short acting melatonin
Mild somnolence occurred in all volunteers, but it was not considered as an adverse event, because just is the therapeutic effect of melatonin
Summary
Melatonin (N-acetyl-5-methoxytryptamine) is a small lipophile molecule that is essentially secreted by the pineal gland and its synthesis shows a circadian pattern (Weaver et al, 1993; Jung and Ahmad, 2006). In addition to the pineal gland, melatonin is synthesized in the retina, bone marrow, gastrointestinal tract, and bile. It has a several functions including regulation of the reproductive axis (Tamarkin et al, 1985; Lang, 1986; Reiter, 1991) regulation of circadian rhythms (Cassone, 1990; Weaver et al, 1993) and antioxidant activity (Reiter et al, 1994). During the day the serum endogenous melatonin concentration is low (10-20 pg/mL), at night reach peak values (80-150 pg/mL) between midnight and 3:00 am. The half-life of melatonin in the serum is 30 to 60 minutes (Waldhauser et al, 1984; Mallo et al, 1990; Cavallo and Ritschel, 1996). Mendoza-Cantú and colleagues investigated the frequency of CYP1A2 5’-flanking region in Mexicans and they found that frequencies are higher than those previously reported for other human populations (Mendoza-Cantú et al, 2004)
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