A COMPARATIVE STUDY OF THE EFFECTIVENESS OF 1,3,7 TRIMETHYLXANTHINE AND CERTAIN DIMETHYLXANTHINES (1,3 DIMETHYLXANTHINE AND 3,7 DIMETHYLXANTHINE) AGAINST FATIGUE

¹ From the Department of Pharmacology and Biological Chemistry, Catholic University of Chile, Santiago de Chile

In cats anesthetized with nembutal a comparative study was made of the actions of 1,3,7 trimethylxanthine (caffeine) and of certain salts of 1,3 dimethylxanthine (theophylline) and 1,7 dimethylxanthine (theobromine), namely theophyllin sodium acetate, theophyllin ethylenediamine, and theobromine sodium salicylate. The study was made of their effects on the quadriceps femoris muscle stimulated indirectly at various frequencies (Section I), and of their effects on the action of prostigmine (Section II) and of curare (Section III)

It was found that all of these drugs have some effectiveness against fatigue and the differences between them are only quantitative. When listed according to the intensity of their action, from least to greatest, they appear thus: at low frequencies: diuretin (theobromin sodium salicylate), theophyllin (theophyllin sodium acetate), aminophyllin (theophyllin ethylenediamine), and caffeine (fig. 1); at higher frequencies: diuretin, aminophyllin, theophyllin, and caffeine (fig. 2).

The effect of these drugs is summated with that of prostigmine (see fig. 4), but diuretin and theophyllin at low frequencies of stimulation produce an intense development of muscular tension (see fig. 3 and Discussion).

All the drugs investigated have a decurarizing action and their effectiveness is in ascending order: aminophyllin, theophyllin, duretin, and caffeine (see figs. 5 and 6).

The mechanism of their action against fatigue is discussed and it is believed that they have the property of lowering the excitatory threshold of acetylcholine at the level of the neuromuscular junction.