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At least 145 records · Page 8Linked to original sources
PubMed1992

Enhanced rectal absorption and reduced local irritation of the anti-inflammatory drug ethyl 4-biphenylylacetate in rats by complexation with water-soluble beta-cyclodextrin derivatives and formulation as oleaginous suppository.

To improve the rectal delivery of ethyl 4-biphenylylacetate (EBA), a prodrug of the anti-inflammatory drug 4-biphenylylacetic acid (BPAA), the use of highly water-soluble 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD) was investigated and compared with the use of the parent beta-cyclodextrin (beta-CyD). Among the three beta-CyDs, HP-beta-CyD was best at improving the rectal bioavailability of EBA in rats after single and multiple administrations of oleaginous suppositories (Witepsol H-5) containing the complexes. To gain insight into the enhancing effect of beta-CyDs, the absorption behaviors of EBA (observed by monitoring BPAA as an active metabolite of EBA) and beta-CyDs themselves were examined in vitro, in situ, and in vivo. The in situ recirculation study revealed that the complexed form of EBA was less absorbable from the rectal lumen in the solution state, but this disadvantageous effect of beta-CyDs was compensated in part by the inhibition of the bioconversion of EBA to BPAA. When beta-CyDs were coadministered with EBA in vivo, however, rather high amounts of HP-beta-CyD (approximately 26% of dose) and DM-beta-CyD (approximately 21% of dose), compared with beta-CyD (approximately 5% of dose), were absorbed from the rat rectum. Thus, the enhancement of rectal absorption of EBA in vivo can be explained by the facts that the hydrophilic beta-CyDs increased the release rate of EBA from the vehicle and stabilized EBA in the rectal lumen and that the drug was partly absorbed in the form of the complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Rectal absorption of nitroglycerin in the rat: avoidance of first-pass metabolism as a function of rectal length exposure.

Nitroglycerin administered orally undergoes substantial presystemic elimination. It was shown recently that first-pass hepatic metabolism of high clearance drugs can be substantially avoided via rectal administration. In applying this concept to nitroglycerin in rats, it was found that unrestricted rectal instillation of nitroglycerin (at 3.5-mg/kg dose) gave a mean +/-SD bioavailability of 26.7 +/- 7.0% (n=6) compared to 1.8 +/- 0.9% (n=5) from oral dosing. This mode of dosing did not lead to complete avoidance of first-pass metabolism of nitroglycerin in rats. When the rectal exposure length to nitroglycerin was restricted to 3.5 cm from the anus, the mean +/-SD bioavailability increased to 83.5 +/- 74.5% (n=14). However, the variability in bioavailability was extremely large. When the rectal exposure length was restricted to 2.0 cm from the anus (at 1.75-mg/kg dose), nitroglycerin bioavailability was estimated at 91.2 +/- 30.4% (n=6). The plasma nitroglycerin concentrations (greater than 5 min) obtained after this mode of administration were similar to those achieved after intravenous dosing. The data showed that substantial avoidance of presystemic nitroglycerin metabolism can be achieved via rectal administration. This avoidance can be nearly complete if nitroglycerin is limited in exposure to only the lower rat rectum. It was also demonstrated that sustained (at least 24 hr) nitroglycerin delivery via the rat rectal route was feasible with an experimental osmotic minipump. This delivery system also produced nearly complete bioavailability for nitroglycerin in the rat.

Animals↗
PubMed1999

Enhanced rectal absorption of insulin-loaded Pluronic F-127 gels containing unsaturated fatty acids.

The objective of this study was to prepare and to evaluate Pluronic F-127 (PF127) gel containing unsaturated fatty acids such as oleic acid (18:1), eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) as a potential formulation for rectal delivery of insulin. The hypoglycemic effect of insulin was examined following rectal administration of the various formulations in normal rats. Rectal insulin absorption was markedly enhanced, and marked hypoglycemia was induced by all PF127 gels (insulin dose, 5 U/kg) containing different unsaturated fatty acids. PF127 gels containing unsaturated fatty acids presented low tmax mean values indicating that the absorption of insulin occurred very rapidly in the rectum. The relative hypoglycemic efficacy of PF127 gel formulations containing fatty acids such as oleic acid, eicosapentaenoic (EPA) and docosahexaenoic (DHA) were 28.4+/-8.1, 26.8+/-14.3 and 23.1+/-5.7%, respectively. The finding demonstrated that 20% PF127 gels containing unsaturated fatty acids are potential formulations for rectal delivery of insulin.

Administration, Rectal↗
PubMed1996

Rectal absorption of omeprazole from suppository in humans.

The oral absorption of omeprazole is incomplete, in part due to first-pass metabolism. We investigated the feasibility of rectal administration of omeprazole by comparing its absorption from a Witepsol H15-based rectal suppository and an orally administered commercial gelatin capsule in 10 male volunteers. Profiles of plasma concentration between two preparations (20 mg) were not statistically different, indicating that the rate and the extent of absorption were similar. Paired t-test revealed no significant differences in area under the curve, mean residence time, and time to peak concentration between two preparations. On the other hand, lag time of absorption and peak concentration were statistically different (p < 0.05) between these preparations. Under these experimental conditions, the rectal route did not produce an improvement in the extent of absorption over an oral capsule.

Area Under Curve↗
PubMed1985

Use of adjuvants for enhancement of rectal absorption of cefoxitin in humans.

The biological availability of cefoxitin administered rectally in the form of suppositories was examined in six human subjects by a cross-over design. Four different suppository systems containing adjuvants expected to enhance the absorption of the drug were studied. The presence of sodium salicylate and a nonionic surface-active agent, Brij 35, gave increased bioavailability as high as 20% compared with 3% for a system without adjuvants. The quantity of sodium salicylate was found to have an influence on the quantity of cefoxitin absorbed, and the salicylate was absorbed over an extended period of time from the rectum. The suppositories were well tolerated, and there were no adverse effects on bowel flora.

Biological Availability↗
PubMed1981

Poor rectal absorption of trimethoprim/sulphamethoxazole in treating Pneumocystis carinii pneumonia.

A 24-year-old female with Hodgkin's disease and Pneumocystis carinii pneumonia was tested with trimethoprim/sulphamethoxazole (TMP/SMX) tablets. Because treatment failure was feared owing to chronic emesis potentially resulting in incomplete drug absorption, the same TMP/SMX dose was administered by rectal suppositories after the 5th day of oral dosing. The relative fractions (rectal/oral) or the suppository dose absorbed for TMP and SMX were 3.0% and 19.5% respectively. When TMP/SMX treatment is required and the oral route is not practical, the investigational i.v. preparation should be obtained.

Administration, Oral↗
PubMed1995

Modification of rectal absorption of morphine from hollow-type suppositories with a combination of alpha-cyclodextrin and viscosity-enhancing polysaccharide.

An attempt was made to optimize the rectal delivery of morphine, using cyclodextrins as an absorption enhancer and polysaccharides as a swelling hydrogel in Witepsol H-15 hollow-type suppositories, and this was tested in rabbits. alpha- and beta-cyclodextrins enhanced the rate and extent of bioavailability, the former being more effective; gamma-cyclodextrin decreased the absorption of morphine. The in-vitro membrane permeation studies using excised rectal sacs revealed that alpha-cyclodextrin enhanced the permeation of morphine through the rectal membranes. In contrast, viscous polysaccharides such as xanthan gum retarded the plasma morphine levels after the rectal administration, reflecting in-vitro slow release characteristics. A combination of alpha-cyclodextrin and xanthan gum produced sustained plasma profiles of morphine along with an increased rectal bioavailability (more than 4 times). From the observation of the distribution behavior of suppositories in rabbit rectum and colon after the rectal administration, xanthan gum was found to prevent the upward spread of the drug. Gross and microscopic observations suggested that this preparation was less irritating to the rectal mucosa.

Animals↗