Differences in the bioavailability of dihydrotachysterol preparations

Abstract

The bioavailability of four preparations containing dihydrotachysterol (DHT₂) was tested in two separate trials with administration of single, oral doses of 1 mg per individual. The relative bioavailability of corresponding preparations (capsules vs capsules and oral solution vs oral solution) was tested in a randomised, crossover pattern within the same group of volunteers. Two different groups of 24 healthy volunteers took part in each trial. Solution and capsule bioavailability was also compared inter-individually. A new sensitive HPLC-method (quantification limit 0.5 ng · ml^-1) was used for the measurement of DHT₂ concentration in serum.

Three of the preparations tested had a similar bioavailability (mean AUC values of 195.5–223 ng · h · ml^-1); the bioavailability of the fourth preparation (A.T.10 oral solution) was considerably lower (mean AUC value 111.5 ng · h · ml^-1). The present dosage recommendations of all four preparations are identical.

A new dosage recommendation is thus required for the oral solution with low bioavailability (A.T.10).