Absorption and excretion of drugs. XXVI. Effect of water-soluble bases on rectal absorption of sulfonamides

Rectal absorption of metronidazole from polyethylene glycol suppositories

The rectal absorption of metronidazole from an aqueous suspension, a fatty suppository and three different polyethylene glycol suppositories was studied in healthy volunteers and compared with absorption from an oral solution. Rectal absorption was found to be rather slow for all suppositories. Of all rectal dosage forms, the polyethylene glycol suppositories gave the highest peak plasma levels and the highest relative bioavailability. Compared with oral administration, a relative bioavailability of 80% could be obtained.

Effects of surfactants on the GI absorption of beta-lactam antibiotics in rats

The effects of various nonionic and ionic surfactants and two bile salts (sodium cholate and sodium taurocholate) on the GI absorption of beta-lactam antibiotics were investigated using the in situ rat GI perfusion technique. Addition of 10 mM polyoxyethylene-23-lauryl ether in the perfusion solution reduced the absorption of propicillin by the stomach and markedly increased the absorption of propicillin and cefazolin by the small intestine. Ester-type nonionic surfactants and bile salts exerted no significant influence on the intestinal absorption of these antibiotics.

The absorption of warfarin from the rat small intestine in situ

The in situ absorption from the rat small intestine of the weakly acidic drug, warfarin (pKa 5-05), at 200 mug ml-1 in the instilled fluid with initial pH levels of 3, 5, 7 or 8 has been examined. These initial pH's in the buffer changed rapidly towards neutrality. The buffers at pH's 3 and 5 probably caused different amounts of warfarin precipitation, which resulted in different rates of warfarin disappearance from the instilled fluid which paralleled the initial rates of accumulation of warfarin in (or on) the intestinal wall. Where greater drug precipitation had probably occurred the initial rates of absorption into the plasma were slower. At the initial pH of 3 and by solubilization of warfarin with propylene glycol, the rate of absorption was similar to that from a fluid of pH 7. Propylene glycol in 15% solution did not affect the system significantly. The relatively high transfer of warfarin into octanol from buffer solution at pH 7 might indicate that the small fraction of unionized drug (1 : 100) at pH 7 is enough for remarkable transfer of this highly lipid-soluble drug.