[Plasma levels, elimination and cumulation of proscillaridin in renal failure (author's transl)]

[Effect of proscillaridin-4'-methylether on pressure rise velocity in the left ventricle of patients with coronary heart disease (author's transl)]

In a randomized, controlled, double-blind study 2 groups of 7 patients each with coronary heart disease received either 1 mg methylproscillaridin (MP) a cardiac glycoside of the squill intravenously, or placebo to test the inotropic effect of MP. Pressures and dp/dt max were measured in the left ventricle before and after coronary angiography after an average of 62 min (60 to 70 min). There was a significant (p less than 0.05) increase of dp/dt max in the MP-group (Wilcoxon-Mann-Whitney test). Left ventricular enddiastolic pressure was decreased from 16.1 to 13.6 mm Hg in the MP-group, and increased in theplacebo group from 12 to 13.7 mm Hg (mean values). Thus, a positive inotropic effect of the glycoside may be assumed.

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.

Digitalis pharmacokinetics and therapy with respect to impaired renal function

The various cardiac glycosides differ significantly in their retention as a result of renal failure. In the case of digoxin, digitoxin, and strophanthin the retention is directly related to the normal renal clearance of these cardiac glycosides: Strophanthin has the highest clearance and the most marked prolongation of pharmacological action in renal failure, whereas digitoxin shows the lowest renal clearance and even in uremic patients a total elimination comparable to normal subjects as a result of increased hepatic clearance; digoxin takes an intermediate position. The quantity of a cardiac glycoside and its metabolites excreted by the kidneys depends, besides the renal clearance, on the plasma concentration which increases considerably during the first days after onset of treatment. From the daily dose approximately 90% of strophanthin, 70% of digoxin, 50% of digitoxin plus metabolites are excreted by normal kidneys under steady-state conditions. The efficiency of hemodialysis in the elimination of cardiac glycosides is low (3-5%) if estimated in relation to a single dose injected before dialysis and high (30-50%) if estimated in relation to the excretory capacity of normal kidneys during a period corresponding to the duration of a dialysis. During hemodialysis the plasma concentration of digoxin decreases as rapidly as in patients with normal renal function. Beside the efficiency of dialysis this finding may be explained by the decrease in the apparent volume of distribution of cardiac glycosides in patients with advanced renal failure; a reduced tissue protein binding seems likely to be the main reason for these changes in chronic renal insufficiency. A reduced volume of distribution and a reduced myocardial sensitivity are the main reasons for a very low predictability of the necessary individual maintenance dose of cardiac glycosides from the creatinine clearance. In patients with advanced renal insufficiency the tolerance to cardiac glycosides is reduced with respect to the daily dose, but it is rather increased in relation to the plasma concentration required to maintain the positive inotropic effect. The combination of hyperkalemia, hypermagnesemia, bypocalcemia and acidosis which is found almost exclusively with chronic renal failure, may explain the reduced myocardial sensitivity. Dosage regimens based on the measurement of creatinine-clearance are of little help in "effective digitalisation". Serial measurements of steady-state plasma concentration of cardiac glycosides may be the only way to reduce the risk of under- and overtreatment in patients with impaired renal function.

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.

Metabolism and excretion of methylproscillaridin by man

0.5 mg 3H-proscillaridin-4-methylether was administered orally to 5 healthy males. Maximum plasma levels of total radioactivity were reached after one to two hours. In two subjects a second peak was observed between 6 and 12 hours. The plasma half life of total radioactivity was 51 hours. 20% and 56% respectively of the dose were eliminated in urine and faeces during the following 7 days. 55% of the total radioactivity in plasma, 80% in urine and 20% in faeces consisted of CHC13-insoluble compounds. 50-60% of the latter in plasma and urine could be hydrolysed by beta-glucuronidase. More than 90% of the split products were identified as conjugates of methylproscillaridin. TLC-separation of the CHC13-soluble fractions of plasma and urine yielded two unidentified metabolites, P2 and P3, as the main compounds, besides methylproscillaridin, proscillaridin and scillarenin. In faeces more than 90% of the non-polar fraction was identified as methylproscillaridin. Shortly after administration of 3H-methylproscillaridin, the radioactivity in plasma consisted mainly of CHC13-insoluble conjugates and of the metabolite P2.