THE DETERMINATION OF THE MINIMAL LETHAL DOSE AND THE AVERAGE RATE OF UPTAKE OF G-STROPHANTHIN AND DIGITOXIN IN THE HEART-LUNG PREPARATION OF THE DOG

¹ Department of Pharmacology, American University of Beirut, Beirut, Lebanon

The effect of rate of administration of g-strophanthin and digitoxin on the L. D., experimental time, destruction and rate of uptake has been studied in the H. L. P. of the dog.

With high rates of administration the L. D. is high. This is due to an overtitration resulting from the inability of the heart to bind all the glycoside offered per unit of time. To determine the M. L. D., rates equal to or lower than the optimal rates of administration have to be employed. The M. L. D. as determined under our experimental conditions is 1.18 micrograms g-strophanthin (0.002 micromols) and 5.95 micrograms of digitoxin (0.008 micromols).

In our experiments it was not possible to detect any destruction of either g-strophanthin or digitoxin by the H. L. P. of the dog.

The dog heart in the H. L. P. binds only an amount of cardiac glycoside equal to the M.L.D. regardless of the concentration in the blood. It was thus possible to calculate the average rate of uptake of g-strophanthin and digitoxin by dividing the M.L.D. by the experimental time. The average rate of uptake thus determined increased with an increase in the rate of administration.