New findings on melatonin absorption and alterations by pharmaceutical excipients using the Ussing chamber technique with mounted rat gastrointestinal segments

https://doi.org/10.1016/j.ijpharm.2009.05.024Get rights and content

Abstract

We examined how melatonin absorption was affected by pharmaceutical excipients using the Ussing chamber technique with mounted rat gastrointestinal (GI) segments. Melatonin absorption occurs throughout the GI tract, with the greatest absorption being in the rectum and ileum and the least in the stomach. Melatonin can be classified as a low permeability drug. P-glycoprotein (P-gp) does not affect melatonin absorption but transported rhodamine 123, a well-known P-gp substrate. The possibility of saturating P-gp by melatonin was excluded. Sodium cholate (0.5%) increased melatonin absorption, but decreased absorption at higher concentrations (1.0% and 5.0%). Sodium oleate (0.5% and 1.0%) consistently decreased melatonin absorption. Pharmaceutical excipients increased the absorption of Lucifer yellow (100 μg/mL), a paracellular probe but decreased the absorption of melatonin above the critical micelle concentration (cmc), suggesting that melatonin was transported mainly by transcellular pathway. Sodium cholate and sodium oleate, when above the cmc, resulted in micellar complexes as revealed by 1H NMR spectra and particle size distribution. Histology tests showed mucosal damage of jejunum tissues in the presence of these excipients. The balance of tissue damage by the formation of micellar complexes could affect the melatonin absorption. This information on melatonin absorption behaviors and its modulation by pharmaceutical excipients can be used in further oral dosage formulations to affect circadian rhythm.

Introduction

Melatonin is an indoleamide hormone that is endogenously secreted by the pineal gland in the brain according to a day–night cycle (Lee et al., 1999). Melatonin acts as a circadian rhythm synchronizer and endogenous antioxidant (Pandi et al., 2006). Oral melatonin preparations are important since exogenous administration of melatonin can be clinically used to maintain/initiate sleep and treat circadian rhythm disorders (Lee et al., 1999). However, the bioavailability of orally administered melatonin preparations in human subjects is limited and variable (Lee et al., 1995). Melatonin is slightly soluble, has good permeability characteristics, and is in the class II category according to the Biopharmaceutics Classification System (Lee et al., 1997, Vlachou et al., 2006). Although the physical properties and numerous oral dosage forms of melatonin have been studied, an understanding of melatonin absorption is very limited. No information about the GI absorption of melatonin and its p-glycoprotein (P-gp) dependency is available.

Drug absorption is a key process governing the in vivo bioavailability of drugs. It is affected by the physicochemical properties of the drug, dosage form, biological state of the gastrointestinal (GI) tract, and co-administered food components (Lee et al., 1997, Wagner et al., 2001). In particular, pharmaceutical excipients can significantly modify physicochemical properties, intestinal permeability, and drug bioavailability when co-administered with a drug (Mithani et al., 1996, Vine et al., 2002, Sharma et al., 2005). Bile acids and fatty acids are generally recognized as safe (GRAS)-listed pharmaceutical excipients and are common components in food and dosage formulations. These excipients have been widely studied as absorption promoters and inhibitors of various drugs. Formation of stable micellar structure could explain changing drug absorption (Yamaguchi et al., 1986b, Sharma et al., 2005). However, no information on the potential modulation of melatonin absorption by these pharmaceutical excipients is available.

The aim of this work was to understand the in vitro absorption behaviors and P-glycoprotein dependency of melatonin using the Ussing chamber technique with mounted rat GI segments. The modulation of melatonin absorption by GRAS-listed sodium cholate and sodium oleate at different concentration levels was also examined.

Section snippets

Materials

Melatonin was purchased from Morepen (New Delhi, India). Absolute alcohol (99.9%) was purchased from Hayman (Witham, England). Sodium oleate, sodium cholate, and sodium chloride were purchased from Sigma (St. Louis, MO, USA). The saline solution (0.9% NaCl) was purchased from Choongwae Pharm. Inc. (Seoul, Korea). Lucifer yellow, Kreb's Ringer bicarbonate buffer and rhodamine 123 were purchased from Sigma–Aldrich (Seoul, Korea). Deionized water was used throughout the study. All other chemicals

Site dependence of melatonin absorption behavior

The site dependency of melatonin absorption through excised rat GI segments at 0.01% melatonin is given in Fig. 1. Melatonin was continuously absorbed and the absorption rate increased as a function of time. The cumulative absorption of a dose of 0.01% (100 μg/mL) melatonin in excised segments of the duodenum, jejunum and colon was similar at about 65.5 ± 3.4 ng/mL after 90 min. The cumulative absorption was the highest in the rectum (157.4 ± 20 ng/mL) followed by the ileum (104.8 ± 5.2 ng/mL) and three

Conclusions

Melatonin absorption occurs throughout the GI tract but shows absorption site dependency. The extent of absorption was highest in the rectum followed by the ileum. However, the absorption behaviors of melatonin are more complicated when simultaneously dosed with excipients. Melatonin absorption varied by the concentration of excipient. Tissue damage, formation of micellar complexes as characterized by 1H NMR analysis, and particle size distribution could affect the melatonin absorption rate.

Acknowledgements

This work was supported by the Korea Science and Engineering Foundation (KOSEF: R01-2008-000-11777-0). We also thank the Central Research Laboratory for the use of the NMR and dynamic light scattering and the Research Institute of Pharmaceutical Sciences, Kangwon National University for allowing the use of their HPLC systems. We would like to thank Dr. Seung Koo Lee for help in examining the histological tests.

References (28)

  • M.J.C. Cebrian et al.

    Intestinal absorption enhancement via the paracellular route by fatty acids, chitosans and others: a target for drug delivery

    Curr. Drug Deliv.

    (2005)
  • E.M. Collnot et al.

    Mechanism of inhibition of P-glycoprotein mediated efflux by vitamin E TPGS: influence on ATPase activity and membrane fluidity

    Mol. Pharm.

    (2007)
  • W. Curatolo et al.

    Safety assessment of intestinal permeability enhancers

  • J.S. Dangi et al.

    Effect of various lipid-bile salt mixed micelles on the intestinal absorption of amphotericin-B in rat

    Drug Dev. Ind. Pharm.

    (1998)
  • Cited by (19)

    • Models to evaluate the barrier properties of mucus during drug diffusion

      2021, International Journal of Pharmaceutics
      Citation Excerpt :

      The permeability value of lucifer yellow (LY, a classic drug transported across the cell bypass) (Rozehnal et al., 2012) is used to correct the permeability value of the drug, and the ratio is more consistent with the in vivo value. Rhodamine 123 (R123) is a well-known P-gp substrate (Tran et al., 2009), which is often used in the study of oral drug absorption and availability. Especially in evaluating the influence of P-gp on drug absorption and secretion.

    • Effects of pharmaceutical excipients on membrane permeability in rat small intestine

      2013, International Journal of Pharmaceutics
      Citation Excerpt :

      Numerous studies on the interactions of drugs and pharmaceutical excipients have been reported, and led to the development of the concepts of pro-drug formulation and drug delivery system (DDS) (Sawada et al., 2003; Takahashi et al., 2005; Alvarez-Lorenzo and Concheiro, 2006). However, there are few reports that focused on the change of gastrointestinal mucosal membrane in association with pharmaceutical excipients (Tran et al., 2009; Merzlikine et al., 2009; Mudra and Borchardt, 2010). Because the influence of pharmaceutical excipients on the gastrointestinal mucosal membrane has not been discussed much (Takahashi et al., 2004; Mudra and Borchardt, 2010), there is very little information about the interaction between gastrointestinal mucosal membrane and different types of pharmaceutical excipient.

    • Melatonin. Comprehensive Profile

      2013, Profiles of Drug Substances, Excipients and Related Methodology
      Citation Excerpt :

      For example, higher concentrations of sodium cholate and sodium oleate decreased melatonin absorption via formation of micellar complexes despite histological tissue damage. The new insights in absorption behaviors of melatonin and effects of common pharmaceutical excipients could be useful for oral dosing in clinical pharmacokinetics as well as designing future oral formulations [213]. Anton-Tay et al. [214] studied i.v. administration of 3H-labeled melatonin (I); the compound was selectively concluded within the hypothalamus and stem portions of the rat brain.

    View all citing articles on Scopus
    View full text