PubMed · 11785703
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T Sanghvi, N Ni, S H Yalkowsky. 2001. A simple modified absorption potential.. https://doi.org/10.1023/a%3A1013347218888
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It was previously found that the bioavailability of Se from Se-rich spirulina (SeSp) was lower than that from selenite or selenomethionine when fed to Se-deficient rats. The present study examined the bioavailability of Se from SeSp subfractions: a pellet (P) issuing from the centrifugation of a suspension of broken SeSp and a retentate (R) resulting from ultrafiltration of the supernatant through a 30 kDa exclusion membrane. Animals were fed a torula yeast based diet with no Se (deficients) or supplemented with 75 microg of Se/kg of diet as sodium selenite (controls) for 42 days. Se-deficient rats were then repleted for 56 days with Se (75 microg/kg of diet) supplied as sodium selenite, SeSp, P, or R. During this period, controls continued to receive sodium selenite. Speciation of Se in subfractions showed that the majority was present in the form of high molecular weight compounds; free selenomethionine was only a minor constituent. Gross absorption of Se from sodium selenite, P, and R was not different and was higher than from SeSp. Only retentate allowed full replenishment of Se concentration in liver and kidney (as did sodium selenite) and glutathione peroxidase (GSHPx) activity in liver, kidney, plasma, and erythrocytes. The bioavailabilities of Se in retentate, as assessed by slope ratio analysis using selenite as a reference Se, were 89 and 112% in the tissue Se content and 106-133% in the GSHPx activities. SeSp and P exhibited a gross bioavailability of <100%. These results indicate that Se in retentate is highly bioavailable and represents an interesting source of Se for food supplementation.
Microemulsion formulations, which can be used to improve the bioavailability of poorly soluble drugs, were designed using only pharmaceutical excipients. Several types of oils and surfactants were tested and it was found that propyleneglycol monoalkyl ester and glycerol monoalkyl ester were solubilized easily in an aqueous medium by various types of surfactants. Although propyleneglycol dialkyl ester was difficult to be solubilized, the solubility was significantly enhanced by mixing it with glycerol monoalkyl ester at the ratio of 1:1. The most suitable surfactants for preparing microemulsion formulations were HCO-40, HCO-60, Tween 80, BL-9EX and Pluronic P84. The use of additional surfactants such as sodium dodecyl sulfate or sodium deoxycholate significantly improved the solubilization capacity of the oils, although formulations free of these surfactants were also available. These microemulsion formulations can be administered as a form of water-in-oil microemulsion or surfactant-oil mixture, and are expected to convert to oil-in-water microemulsion in the small intestine.
The buccal administration of ergotamine tartrate (ET) combined with polyvinyl alcohol (PVA) gel brought about higher plasma concentration of ET compared with that of oral administration of capsules in guinea-pigs. T(max) of ET in plasma of buccal administration was significantly smaller than that of oral administration. For the buccal dosage form of ET, the bioadhesive tablet system (BTS) was newly developed. It consisted of a reservoir of drug and an adhesive region. BTS showed better absorption of ET compared with PVA gel in guinea pigs. Among several pharmaceutical bases in the reservoir of BTS, Witepsol W-35 was most effective. It is likely that the high lipophilic property of Witepsol W-35 in which ET was dissolved facilitated the drug release by its relatively low melting point (around 35 degrees C), consequently a rapid absorption. In addition, the enhancing activity of the cod-liver oil extract (CLOE) in hydrophilic ointment on the in vivo buccal ET absorption was clarified to be comparable to that in the in vitro study utilizing the keratinized epithelial-free membrane (KEF-membrane) of the hamster cheek pouch.