Bile salt enhancement of riboflavin and flavin mononucleotide absorption in man.

The gastrointestinal absorption of riboflavin and flavin mononucleotide (FMN) was determined under control conditions and after oral administration of 600 mg sodium deoxycholate. When the bile salt is given prior to a 30-mg dose of riboflavin there is a 50 to 80% increase in total urinary recovery of apparent ribo flavin. A similar, but less marked, enhancement is observed when the same dose of FMN is given with sodium deoxycholate. Urinary excretion data also suggest an unusually prolonged absorption of riboflavin in the presence of the bile salt. The possibility exists that the bile salt enhancement of riboflavin and FMN absorption may be due to changes in gastrointestinal motility or changes in the permeability of the gastrointestinal membranes to the transport of the vitamins, or both. Other possibilities are also explored. Although the human nutritional require ment for riboflavin has been recognized for some time, speculation still exists con cerning the gastrointestinal absorption of this vitamin. Morrison et al. ( 1) have sug gested that riboflavin is absorbed high in the human intestinal tract based upon the observation that peak urinary excretion values were obtained within 2 hours after oral administration of riboflavin in solu tion or in sustained release form. Lane et al. (2) reported that the percentage of the administered dose of riboflavin re covered in the urine (which reflects the percentage of dose which is absorbed) following oral administration, decreased with increasing dose. The latter observa tion was confirmed by Stripp (3), who also showed that not more than 14 to 18 mg of riboflavin are excreted in the urine, independent of oral dose of riboflavin or flavin mononucleotide (FMN) when the dose exceeds 50 mg. More recently, Levy and Jusko studied die gastrointestinal ab sorption of riboflavin (4) and FMN (5) in man and suggested the existence of a spe cialized transport process for the vitamin in the upper region of the intestinal tract. The absorption of several nutrients may be strongly influenced by bile salts, an important class of physiological surface active agents. Extensive research has in dicated the importance of bile salts in lipid absorption (6-8). In addition, there have been several studies implicating bile salts in the absorption of water-insoluble vitamins. These reports demonstrate that the absorption of vitamins A (9â€”11), D (12-14) and K (15) is enhanced by the presence of various bile salts. Bates et al. (16-18) have suggested, based on solubilization and dissolution studies of several water-insoluble drugs, that bile salts may influence drug ab sorption by enhancing dissolution rate. Cavallito and O'Dell (19) studied the in fluence of coadministration of sodium cholate and dehydrocholate on the pharma cologie response to a quaternary hypotensive agent in dogs. In each case an apparent increase in drug absorption was suggested by the enhanced pharmacologie response. Davenport (20) reported that sodium taurocholate and natural bile markedly disrupt the gastric mucosal bar rier in dogs as evidenced by changes in ionic fluxes. Studies with isolated intesti nal segments have shown the influence of bile salts on nutrient (21) as well as drug