Studies on South African cardiac glycosides. II. Observations on the clinical and haemodynamic effects of cotyledoside

Abstract

Cotyledoside, a bufadienolide isolated from Tylecodon wallichii (Harv.) Toelken, subs. wallichii (=Cotyledon wallichii Harv.), was dosed to guinea-pigs and sheep. In guinea-pigs, the oral and subcutaneous LD₅₀ values were very similar (cf. 0,173 mg/kg over 48 h with 0,116 mg/kg over 24 and 48 h). When dosed subcutaneously, a cumulative effect was observed. Intravenous administration of cotyledoside to anaesthetized guinea-pigs resulted in: dyspnoea, increased heart rates and blood pressures, and electrocardiagraphic changes typical of cardiac glycoside poisoning. A positive cardiac inotropic effect was succeeded by a positive chronotropic one. In sheep, acute and subacute intoxication resulted in ruminal, respiratory and cardiac changes. The signs included ruminal stasis, cyanosis, cardiac arrhythmia, ectopic foci and AV dissociation, followed by hypotension and progressive respiratory and cardiac failure. The skeletal muscles were affected in only 1 sheep vide infra. In chronically intoxicated sheep typical clinical signs of "krimpsiekte" developed, e.g. weakness, reluctance to stand, unsteadiness on feet, tremor and paresis of hindquarter muscles, paresis of the neck, arching of the back and standing with the feet close together. Respiratory function was affected in all 3 cases; ruminal stasis, with concomitant loss of appetite occurring in one, and a transient change in heart function in another. The syndrome induced by acute cotyledoside poisoning is similar to that of other cardiac glycosides, but the paretic signs of chronic intoxication resemble "krimpsiekte", a disease associated only with intoxication with the plants of the family Crassulaceae.