A COMPARATIVE STUDY ON SOME PHARMACOLOGICAL EFFECTS OF DIGITOXIN, ACETYLDIGITOXIN AND GITALIN (AMORPHOUS) IN CATS

The lethal doses of digitoxin, acetyldigitoxin and gitalin were determined in cats. Electrocardiograms were recorded intermittently during the course of the repeated injections of these glycosides. Their relative lethal activities in cats were found to be similar to the reported relative therapeutic activities in man. Gitalin was found to be significantly more liable to cause cardiac arrhythmias than the other two glycosides.

Preliminary chemical examination of digitalis tissue cultures for cardenolides

Three Digitalis species were grown as callus or suspension tissue cultures, extracted and examined by paper chromatography. Kedde-positive substances (cardenolide glycosides) were found.

Chemical Studies of the Leaves and Inflorescences of Digitalis Purpurea L. and of Allied Species

The total glycoside content and the nature of the individual glycosides in the leaves and inflorescences of Digitalis purpurea, D. lanata, D. lutea, D. thapsi and D. ambigua have been studied. A similarity in the chemical composition of the leaves and inflorescences of each species has been demonstrated. The yield of glycosides from D. purpurea and from D. thapsi would be increased by harvesting the entire aerial parts of the second year plants.

Digitalis: a dangerous drug in atrial fibrillation? An analysis of the SPORTIF III and V data

OBJECTIVE

In heart failure, digitalis increases exercise capacity and reduces morbidity, but has no effect on survival. This raises the suspicion that the inotropic benefits of digitalis may be counteracted by serious adverse effects. Patients with atrial fibrillation (AF) were studied to clarify this.

DESIGN

In the Stroke Prevention using an ORal Thrombin Inhibitor in atrial Fibrillation (SPORTIF) III and V studies, 7329 patients with AF at moderate-to-high risk were randomised to preventive treatment of thromboembolism, either with warfarin or the oral direct thrombin inhibitor ximelagatran. The survival of users and non-users of digitalis was investigated.

RESULTS

At baseline, 53.4% of the study population used digitalis, and these patients had a higher mortality than non-users (255/3911 (6.5%) vs 141/3418 (4.1%), p<0.001; hazard ratio (HR) = 1.58 (95% CI 1.29 to 1.94)). Digitalis users also had more baseline risk factors. After multivariate risk factor adjustment, the increased mortality persisted (p<0.001; HR = 1.53 (95% CI 1.22 to 1.92 vs 1.23 to 1.92)).

CONCLUSIONS

The results suggest that digitalis, like other inotropic drugs, may increase mortality. This may be concealed in heart failure, but be revealed in patients with AF, who need the rate-reducing effect of digitalis, but do not benefit much from an increased inotropy. Cautious interpretation of the data is mandatory since the patients were not randomised with respect to digitalis use.

Predictors of Mortality and Hospitalization in Women with Heart Failure in the Digitalis Investigation Group Trial

We performed a retrospective follow-up study of 1926 women with heart failure who participated in the Digitalis Investigation Group trial. Adjusted hazard ratios and 95% confidence intervals for covariates that were significant independent predictors of all-cause mortality were age in years (1.02; 1.01-1.03; P<0.001), NYHA class IH-IV (1.56; 1.31-1.87), diabetes (1.63; 1.36-1.95), glomerular filtration rate in mL/min/1.73 m(2) (0.99; 0.98-4).996; P=0.001), pulmonary congestion by chest x-ray (1.57; 1.22-2.02), left ventricular ejection fraction (LVEF) (0.99; 0.98-0.993; P<0.001), and use of digoxin (1.20; 1.02-1.42). Covariates that were significant independent predictors of hospitalization due to worsening heart failure were: nonwhite race (1.28; 1.03-1.58), NYHA class III-IV (1.55; 1.30-1.84), diabetes (1.75; 1.47-2.09), glomerular filtration rate as mL/min/1.73 m(2) (0.99; 0.986-0.996; P<0.001), pulmonary congestion by chest x-ray (1.42; 1.12-1.81), and use of ACE inhibitors (0.67; 0.49-0.91). Longer duration of heart failure, higher NYHA classes, diabetes, chronic kidney disease, pulmonary congestion, and lower LVEF were significant independent predictors of all-cause mortality, all-cause hospitalization, and hospitalization for heart failure in women with heart failure.

William Withering's legacy--for the good of the patient

The lessons that the physician William Withering learned from his studies of digitalis are still relevant today. This paper highlights four of these lessons and updates them using the tools of clinical pharmacology and pharmacoepidemiology. First, Withering learned that failure to prepare digitalis from the foxglove in a standard manner resulted in a product with unpredictable clinical effects. Preparation of medicines from plants since then has not followed similar good practice and medicines have often not been granted marketing authorisation because of variability in their quality. Second, differences in the response to digitalis were noted by Withering, but he had little idea of their basis. Clinical pharmacology has shown that for drugs such as digitalis differences are caused by variability both in receptor sensitivity and in drug disposition. Third, the dose-response characteristics of digitalis were well known to Withering. Modern techniques of measuring response, such as the use of biomarkers, have made such studies easier, although clinical observations remain the gold standard. Fourth, Withering documented many of the adverse effects of digitalis. The use of various modern databases has facilitated the analysis of clinical toxicology and thus of risk-benefit profiles.

Lunar Society and the discovery of digitalis

William Withering was an established member of the renowned Lunar Society as well as an accomplished physician and botanist. Withering was an obsessive note taker and had a compulsion to observe and record. At the time when bleeding was the most common form of treatment for "dropsy", Withering's discovery of the foxglove and his detailed description of its medicinal purposes represented a major advance in the treatment of patients with heart failure. Withering's scrupulous account of the foxglove's potential for treating conditions of the heart was derived from dedicated study, experimentation, and deep concern for detail. The publication of "An Account of the Foxglove, and Some of its Medical Uses: with practical remarks on dropsy, and other diseases" marks a defining moment in the history of medicine.