TY - JOUR T1 - VARIATIONS IN BLOOD PRESSURE ON REPEATED ADMINISTRATION OF <em>l</em>- AND <em>dl</em>-EPHEDRINES JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 219 LP - 235 VL - 33 IS - 2 AU - K. K. CHEN Y1 - 1928/06/01 UR - http://jpet.aspetjournals.org/content/33/2/219.abstract N2 - 1. Repeated intravenous injections of natural (l-) or synthetic (dl-) ephedrine in anesthetized, decerebrated, or pithed cats, dogs and rabbits, result in gradual loss of pressor action and finally a transient fall of blood pressure. The same phenomenon can be observed if l-ephedrine is repeatedly injected following the first dose of dl-ephedrine: or vice versa. 2. The gradual loss of pressor action is due to the advancing failure of cardiac stimulation, while the reversal is due to cardiac depression. 3. In men, the first tolerated dose of l- or dl-ephedrine given by mouth usually produces the greatest pressor response, while subsequent doses of the same size administred by the same route at two-to three-hour intervals have a summating and sustaining effect. Single doses of ephedrine, given over twenty-four-hour intervals, do not appear to have any influence on each other. 4. Compared with epinephrine, there have been found points of difference in the action of ephedrine, the gradual decrease of the pressor effect and the reversal being one of them. These difference are, however, not sufficient to exclude ephedrine from the class of sympathomimetic amines. ER -