Absorption of beta-methyl-digoxin determined after a single dose and under steady state conditions

Pharmacokinetics of beta-methyldigoxin in subjects with normal and impaired renal function

Beta-methyldigoxin (beta-MD) was administered orally (0.2 mg) to 24 patients with various degrees of renal function, to investigate its pharmacokinetic characteristics related to renal function. Serum and urine collected until 120 hours after dosing were assayed for beta-MD and digoxin by high-performance liquid chromatography and fluorescence polarization immunoassay method. The steady-state volume of distribution decreased proportionately as creatinine clearance (CLCR) decreased, although steady-state volume of distribution of hemodialysis patients had large interindividual variability, and their mean value was not different from that of patients with normal renal function. Both renal clearance of beta-MD and digoxin were significantly correlated with CLCR (r = .820, P < .001 and r = .822, P < .01, respectively), and the slope of regression line for beta-MD was only 44% that for digoxin. Significantly reduced urinary excretion of total drug (beta-MD plus digoxin) was shown in patients with CLCR below 50 mL/minute/1.48 m2. This study suggests that the dosage modification is not necessary until CLCR decreases to below 50 mL/minute/1.48 m2, but careful attention should be given in the use of beta-MD in patients with CLCR below this value.

A collection of therapeutic, toxic and fatal blood drug concentrations in man

In order to assess the significance of drug concentrations measured in clinical and toxicological investigations, it is essential that good collections of data are readily available. As a guide to interpreting findings, the present work provides a compilation of therapeutic, toxic and fatal blood concentration ranges of 298 drugs of interest to clinical pharmacologists, clinical toxicologists, and forensic toxicologists. Wherever possible, ranges are expressed concisely in terms of the maximum blood concentrations which account for 10, 50 and 90% of the data collected. They provide easy access to the most reliable information which relates the blood drug concentration to the biological response it produces. Where appropriate, the different toxic effects of a drug and/or the different degrees of severity of toxic symptoms associated with different drug levels are clearly defined. The original sources of all data used are provided to allow the analyst to obtain further analytical, pharmacokinetic and toxicological information should this be necessary. Those factors (e.g. age, capacity for drug metabolism, drug interactions, etc) which can modify the relationship between a drug concentration and the response it produces are briefly discussed.

Comparative pharmacokinetics and pharmacodynamics of cardiac glycosides

1 The pharmacokinetics and pharmacodynamics of ouabain, digoxinn and beta-methyl digoxin (medigoxin) have been investigated in a crossover study in four normal healthy volunteers. 2 Pharmacokinetics were studied using [3H]-labelled glycosides and the shortening of the left ventricular ejection time (LVET) was used as a measure of the effect of the drugs. A graded exercise protocol was used to correct for the effects of heart rate on LVET. 3 In three of the four subjects, both digoxin and beta-methyl digoxin produced a shortening in the LVET, but no such change could be detected with ouabain in any of the four subjects. 4 There was a good linear correlation between the shortening of the LVET and the amounts of digoxin or beta-methyl digoxin present in the body tissues. 5 One subject who showed no drug-related LVET shortening had greatly enhanced clearances of all three drugs studied.