Pharmacokinetics of prifinium bromide in healthy volunteers

The pharmacokinetics of prifinium bromide (Riabal), a specific antispasmodic agent, after oral (60 mg) and i.v. (7.5 mg) administration was studied in six healthy male volunteers. After i.v. administration, the drug was rapidly cleared from the serum. Individual serum levels were described by a bi-exponential equation and mean elimination half-life was 2.13 h. The volume of distribution at steady state was about 190% of body weight, and the total serum clearance and renal clearance were 12.5 and 5.80 ml/(min. kg), respectively. The drug reached maximum serum levels (6.76-14.3 ng/ml) within 2-3 h after administration of tablets: the apparent biologic half-life after oral dosing was 2.18 h. The oral bioavailability was low (3.4%), as expected for quaternary ammonium compounds, but the inter-individual variation of bioavailability was small.