The gastrointestinal absorption of anticholinergic drugs: comparison between individuals

Discontinuous oral absorption of cimetropium bromide, a new antispasmodic drug

The pharmacokinetic profiles of cimetropium bromide, after either intravenous injection of 10 mg or oral ingestion of 200 mg, were determined in eight healthy volunteers. After intravenous administration, the plasma levels and urinary excretion indicated that the drug is distributed and eliminated at a rapid rate (terminal half-life, 50 +/- 8 min) and that urinary excretion is not the exclusive route of elimination (46 +/- 2%) of the administered dose). After oral administration, a low percentage of the drug is absorbed (1-4% of the administered dose), however, the amount is sufficient for therapeutic effect. The absorption is discontinuous, with two distinct phases, and ends abruptly during the second phase.

Human studies on the bioavailability of a quaternary ammonium compounds, tiemonium iodide and tiemonium methosulphate

Five volunteers were administered capsules containing 14C-labelled tiemonium iodide and 4 volunteers received capsules of 14C-labelled tiemonium methosulphate. Serum, urine and faecal levels of tiemonium were measured. The percentage of the dose absorbed was determined after a further labelled intravenous injection into 3 of the volunteers. The drug appeared to be poorly absorved, as expected for quaternary ammonium compounds, but there was no difference in the bioavailability of these two tiemonium salts.

Intestinal absorption, intestinal distribution, and excretion of (14C) labelled hyoscine N-butylbromide (butylscopolamine) in the rat

Butylscopolamine was labelled with 14C and its gastrointestinal absorption, biliary and urinary excretion, enterohepatic circulation and gastrointestinal distribution were examined in anaesthetized rats. Biliary excretion was the main elimination route of intra-portally administered [14C]butylscopolamine, with 42% of the dose recovered in the bile during 12 h. About 6% of the radioactivity administered orally as [14C]butylscopolamine was excreted in the bile and 1.2 % in the urine during 24 h, which indicates poor gastrointestinal absorption of butylscopolamine in the rat. When collected radioactive bile was readministered intrajejunally, only about 7% of the radioactivity was recovered in bile and urine during 12 h, which suggests that only a small fraction of butylscopolamine and its metabolites engage in an enterohepatic circulation. After oral administration of [14C]butylscopolamine, radioactivity was found to accumulate in the wall of the distal small intestine, and about 20% of the dose was found in this tissue 24 h after drug administration. As a result, local anti-acetylcholine effects of butylscopolamine might be expected.