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Biomedical subjects

T Nishihata

Publications and source records attributed to T Nishihata.

At least 91 records · Page 5Linked to original sources
PubMed1982

Enhanced rectal absorption of theophylline, lidocaine, cefmetazole, and levodopa by several adjuvants.

Ten potential adjuvants for rectal absorption which are structurally similar to salicylate have been examined using an in situ perfusion of the rat rectum technique as well as an in vivo absorption method from microenemas. All of the adjuvants studied readily disappeared from the perfusate at pH 4.5; however, several were not absorbed well at pH 7.4. Only those that were lost rapidly from the perfusate at pH 7.4 were effective in enhancing the disappearance of the drugs (theophylline, lidocaine, cefmetazole, and levodopa) at either a pH of 4.5 or 7.4. The compounds that were effective in promoting the disappearance of drugs from the rectal perfusate all had hydroxy and carboxy groups. Those substances lacking a hydroxy group were not effective. The binding of these potential adjuvants and salicylates to rat rectum tissue was studied by equilibrium dialysis. Those adjuvants with relatively high binding to rat rectal tissue were better absorbed themselves and promoted the disappearance of drugs more than those substances exhibiting little binding. Thus, adjuvant binding to some feature of the rectal membrane appears to be important in the enhanced absorption of drugs from the rectum under the conditions of this study.

Adjuvants, Pharmaceutic↗
PubMed1982

Effect of salicylate on the rectal absorption of lidocaine, levodopa, and cefmetazole in rats.

Salicylic acid and sodium salicylate have been found to enhance the absorption of lidocaine, levodopa, and cefmetazole after rectal administration to rats. These drugs represent a base (lidocaine), an acid (cefmetazole), and a substance (levodopa) which exists as a zwitterion in solution. The rectal absorption of each type of drug, as well as theophylline, a neutral compound, was enhanced by salicylate, particularly at pH values where the substances exist primarily in their ionic form. A requirement for the observed enhancement is that salicylate be present in the rectal membrane. The loss of drug from the perfusing solution was greater from solutions having an ionic strength of 0.75 than from those with mu = 0.15.

Animals↗
PubMed1981

Effects of salicylate on rectal absorption of theophylline.

The rectal absorption of theophylline in rats was facilitated by concurrent administration of salicylic acid or sodium salicylate. The absorption of theophylline depended on the simultaneous absorption of salicylate and increased with an increasing concentration of salicylate. Calcium and magnesium ions inhibited the effects of salicylate at pH 7.4 but not at pH 4.5. Sodium lauryl sulfate caused lasting changes in rectal absorption, whereas the effects of salicylate on absorption were observed only when salicylate was present Strong chelating agents, such as ethylenediaminetetraacetic acid and sodium citrate did not effect the absorption of theophylline, except at very high concentrations (30%), where membrane damage was observed. Rectal drug absorption was not enhanced by vasodilation or inflammation alone since sodium nicotinate and histamine did not facilitate the disappearance of theophylline from the perfusate.

Animals↗
PubMed1981

Enhanced intestinal absorption of insulin in rats in the presence of sodium 5-methoxysalicylate.

Sodium 5-methoxysalicylate, previously shown to enhance the rectal absorption of several drugs, facilitates the absorption of insulin from the upper gastrointestinal tract, resulting in significantly elevated insulin levels and lowered glucose concentrations in the plasma of rats. Restricting the movement of insulin and adjuvant down the intestine by either ligation or use of a more viscous vehicle further increased the absorption of insulin.

Animals↗