A contribution to the pharmacokinetics of bencyclane (Fludilat) in man

The quantitative determination of bencyclane from the biological material was carried out with the aid of a combined microchemical method (thin-layer chromatography and measurement of fluorescence) using NBD chloride. The original method [J. Reisch, Z. Analyt. Chemie, 247 (1969) 56; J. Monforte, Clinical Chemistry 18 (1972) 1329; R.S. Fager, Anal. Biochemistry, 53 (1973) 290, etc.] was so modified as to enable attainment of optimal results in respect of sensitivity and accuracy in the determination of bencyclane. The sensitivity of this modified method is 0.1 mug/ml plasma. Volunteer subjects and patients received under standard conditions 2 coated tablets Fludilat (i.e. 200 mg bencyclane hydrogen fumarate) orally as a single dose or repeated 3 times daily over 5 days, or 4 ampoules (= 200 mg) in a single intravenous injection. After a single oral administration, maximum plasma concentrations of approximately 2 mug/ml were attained in about 2 hours. The elimination half-life was about 360-480 min. The appearance of a second peak after about 6-7 hours indicates involvement of several compartments. On intravenous administration, maximum plasma concentrations of above 2 mug/ml were attained. A second peak in the late phase of the elimination was also detected here. The repeated oral administration led to maximum plasma concentrations of above 3 mug/ml without there being any indication of accumulation. Protein binding of about 30% was determined with the aid of the equilibrium dialysis method. A parallel "in vitro" study with 14C-bencyclane (U.R. Kleeberg, 1973, unpublished) showed an approx. 40% protein binding, an approx. 30% erythrocyte binding, and an approx. 10% thrombocyte binding. About 20% bencyclane remain free.