Plasma levels after a single oral dose of proscillaridin

Proscillaridin activity in portal and peripheral venous blood after oral administration to man

The absorption of proscillaridin A was studied in four patients undergoing catheterization of the portal vein for diagnostic purposes. Proscillaridin 1.5 mg was given as a single oral dose and plasma glycoside activity was analyzed by the 86Rb-uptake inhibition technique. Proscillaridin appeared rapidly in the portal blood, peak activity being found after 15 min in three and after 30 min in one patient. In peripheral blood the peak activity occurred after approximately 35 min. Despite rapid passage across the gut wall, porto-peripheral differences in glycoside activity were small; they were zero after 4h. The mean amount absorbed as active porscillaridin during the first 4h after the dose was calculated to be only 7.1% of the given amount. Late porto-peripheral differences, probably due to enterohepatic recycling, appeared after 6h in three patients; The results suggest that proscillaridin undergoes first pass inactivation in the gut wall. Enterohepatic recirculation may contribute to the amounts of active glycoside that reach the systemic circulation.

Biliary excretion and enterochepatic recycling of proscillaridin A after oral adminstration to man

A single oral dose of proscillaridin A (1.0-1.5 mg) was given to six patients with T-tube drainage of the common bile duct, and simultaneous samples of bile and plasma were collected at various times during the following 24 hours. Glycoside activity was assayed by the 86Rb-uptake inhibition technique. Peak activities in plasma (mean 0.80 ng/ml) were attained after 0.5-2h, and in bile (mean 6.9 ng/ml) after 1-4h. Subsequently, proscillaridin activity in bile was less than 5 ng/ml for the remainder of the sampling period, and 10-100 times higher than that in plasma. Bile samples treated with beta-glucuronidase and sulphatase showed 100-200 fold increase in glycoside activity. Deconjugation was also produced by treatment with enteric contents. The results suggest that conjugation of unchanged proscillaridin is a major metabolic route. After excretion in the bile, the conjugates may be split in the intestine and reabsorbed as active glycoside.

Activities of proscillaridin A in thoracic duct lymph after single oral doses in man

In order to study the possibility that orally administered proscillaridin after absorption is transported by the lymph to the systemic circulation, the concentrations of the glycoside in thoracic duct lymph were analyzed in two patients with thoracic duct drainage. They received the drug as a single oral dose; plasma and lymph concentrations were measured by 86Rb-technique. Lymph was collected at various intervals for 24 hrs. The proscillaridin activity in thoracic duct lymph was low and followed closely that the plasma. During the sampling period, a total of 300 ng and 240 ng, respectively, was recovered in the lymph, corresponding to less than 0.03% of the administered dose. The results indicate that proscillaridin is not transported by the thoracic duct lymph.

On the absorption of proscillaridin A after single oral doses to normal and achlorhydric subjects

Proscillaridin A was given in single oral doses (1.5-2.5 mg) to normal and achlorhydric subjects. Plasma activities of the glycoside were analysed by 86Rb-technique. The absorption pattern was similar in both groups. A marked first peak of proscillaridin activity was seen after about 30 min. After a first minimum, a second peak of activity was registered within 6-12 hrs. An estimate of the amount of active glycoside absorbed during the first 12 hrs after the administration was obtained by calculating the areas under the plasma activity curves (AUC). When corrected for differences in dose per kg body weight, the mean AUC in the achlorhydric group was about 60 per cent greater than in the normal group. The results suggest that proscillaridin is rapidly absorbed; gastric acidity seems to contribute to inter-individual differences in the bio-availability of the glycoside.

Pharmacokinetics and pharmacodynamics of methyl proscillaridin in healthy man

The aim of this study was to obtain data about the pharmacological properties of a new glycoside derivative in man. Plasma concentrations and ECG parameters were measured after oral and intravenous administration of a single dose of 1.2 mg methyl proscillaridin in 16 healthy volunteers, using a strictly randomized, two-period change-over design. Glycoside concentrations were measured using a modified 86Rb-erythrocyte-assay. QT-duration, corrected for frequency (QTc), was the principal variable measured in the ECG. By either route, there was a maximum plasma level after 1 hour, which had decreased to a minimum at 3 hours, followed by a second peak at 4 to 10 hours (orally greater than iv). From 10 to 72 hours the concentrations decreased with a median t 1/2 of 23.3 hours (iv) and 33.0 hours (orally). Comparison of the ratio of plasma concentrations following oral and iv administration resulted in a bioavailability of 69% using the 48 hour plasma levels, and 59% using the areas under the concentration-time curves. The mean QTc was maximally shortened to 28 msec at 1 hour after iv and to 19 msec at 10 hours after the oral dose. A distinct similarity between time-concentration and time-QTc curves was seen after the initial distribution phase, both after oral and intravenous administration. The new derivative shows a rapid elimination. Its bioavailability is reasonably high.

On the pharmacokinetics of proscillaridin A in man

The plasma concentration of proscillaridin was measured by a modified 86Rb method during treatment with multiple doses of a commercial preparation of proscillaridin. Despite high doses, very low plasma levels were found, and there were only minute amounts of glycoside activity in urine and faeces. Administration of an enteric-coated proscillaridin preparation gave higher plasma levels, which raises the possibility of inactivation of the glycoside by acid gastric juice. The results suggest that proscillaridin has low biological availability when given orally, and that it is extensively metabolised in the body.

Half-life plasma following repetitive application of beta-acetyl digoxin in man

The aim of this study was to determine the half-life of beta-acetyl digoxin in plasma after cessation of its continous oral application. 18 healthy male volunteers received 0.4 mg p.o. of beta-acetyl digoxin daily for a period of 14 days. Plasma glycoside concentrations were measured up to 108 hours after the last application utilizing a 86Rb-erythrocyte assay. Mean plasma digoxin concentration 12 hours after the alst dose was -x=1.05 ng/ml, sx=0.301. Mean half-life in plasma was 55.8 hours (sx=21.7). This corresponds to a mean daily elimination rate of abour 25.8%. These results are in good agreement with the 20% loss of effect on the heart as reported in the literature.