Dihydroergotoxine kinetics in healthy men after intravenous and oral administration

Pharmacokinetics and bioavailability of ergoloid mesylates

The pharmacokinetics and bioavailability of ergoloid mesylates following single administrations of various dose levels (3-9 mg), dosage forms (oral swallow and sublingual tablets, solution) and under different dosing conditions (fasted, with meal) were studied in young healthy volunteers. Male and female subjects showed a similar rate and extent of bioavailable ergoloid after drug treatment. The absorption of ergoloid using either the tablet dosage forms or the drug administered as a solution was rapid, with peak levels of about 60-80 pg ml-1 mg-1 dose achieved after 0.6 to 1.3 h. The elimination half-life for ergoloid in plasma was 2-5 h. Administration of drug with food had no effect on the extent of absorption (AUC) but lowered the absorption rate. This resulted in a reduction of (by 25 per cent) and delay in (by 1 h) achieving peak levels (Cmax). Increasing the ergoloid dose caused a proportional increase in the AUC, but a smaller than proportional increase for Cmax. The tablet formulations provided similar AUCs as the solution; the objective of the sublingual tablet formulation to provide improved bioavailability over the swallow tablet via circumvention of first-pass metabolism was therefore not realized. Transient decreases in blood pressure after ergoloid treatment paralleled the plasma level profiles. Higher ergoloid levels were paired with the larger pressure decreases.

The absolute systemic availability of a new oral formulation of co-dergocrine in healthy subjects

We have studied the absolute systemic availability (f) of an oral formulation (Hydergin spezial = Hydergine FASR 4 mg per tablet) of co-dergocrine by three different methods. Twelve healthy volunteers received single doses of 0.9 mg co-dergocrine intravenously and 8.0 mg orally in a randomized crossover design. The pharmacological effect of co-dergocrine was monitored as a reduction in plasma prolactin. Maximal plasma concentrations of co-dergocrine after oral dosing ranged between 0.181 and 1.307 ng.ml-1. Maximal urinary excretion ranged between 4.7 and 9.9 micrograms.h-1 and between 0.3 and 2.3 micrograms.h-1 after intravenous and oral doses respectively. Clearance was measured as 90 +/- 22 l.h-1 and the absolute systemic availability (f) as 2.25 +/- 0.65% by using the areas under the plasma concentration-time curves extrapolated to infinity. Calculation of f by comparing areas up to 32 h or the fractions of the dose excreted in urine led to identical results. The intravenous and oral doses produced similar pharmacological effects (reduction of plasma prolactin concentrations) despite the small value of f.

Bioavailability of dihydroergosine in healthy volunteers

Eight healthy volunteers received an oral dose of 10 mg and an intravenous dose of 0.75 mg of dihydroergosine. Plasma concentrations were measured by HPLC method, and some pharmacokinetic parameters were calculated. The biologic half-life in the elimination phase was 8.35 +/- 1.87 h after oral administration and 8.84 +/- 3.64 h after intravenous administration. In both cases of administration a secondary rise in plasma concentration of dihydroergosine was observed, which can be attributed to hepatic recycling. The calculated bioavailability of the drug was 9.80 +/- 2.8%.

Absorption kinetics of dihydroergotoxine following oral administration to man

The absorption characteristics of dihydroergotoxine administered as an oral solution, tablet and retard capsule have been determined in a randomised cross-over investigation in 12 healthy males. The plasma concentrations of dihydroergotoxine produced by the three preparations, measured using a specific and sensitive radioimmuno-assay method over 24 h, exceeded 200 pg ml-1 for approximately 5 h and decayed in a biphasic manner with a slowest measured half-life of 12-14 h. The retard capsule differs from the other two preparations in having a low Cmax (50% of that recorded for the solution) and a clearly defined plateau. The bioavailability of the retard capsule was similar to that for the solution indicating that first-pass metabolism is not significantly increased following a three-fold prolongation in the absorption rate constant. The 20-40% greater bioavailability of dihydroergotoxine solution and retard capsule in comparison with the standard tablet may be due to a reduced contact time with gastric secretions achieved by means of rapid absorption from the stomach (solution) or delayed release at pH 1.5 (retard capsule).

Plasma kinetics of dihydroergotoxin in rat by using a radioreceptor assay

A radioreceptor assay (RRA) (with brain dopamine receptors) has been developed to determine the levels of dihydroergotoxin-equivalent (DHT-equivalent) material in rat plasma and its kinetics after oral and i.v. administration (5 mg/kg). After i.v. administration the plasma kinetics follows a two-exponential equation, with an apparent distribution volume of 7-9 1/kg and a long half-life (about 36 hours). The kinetics of DHT after oral administration shows two peaks; this could indicate a biliary recycling of the drug and/or of its metabolites. The low bioavailability (19%) and the biliary recycling of DHT-equivalent material suggest a first pass effect.