Acta Med Scand zyxwv 205: 49-52, 1979 Effects of Some Cardioactive Drugs on the Oxygen Affinity of Whole Blood Kerstin Berntorp, Stig Berglund and Bengt W. Johansson zyxw From the Department zyxwvutsr of Internal Medicine I und the Heart Section, Mulmii General Hospitul, Malmii, Sweden ABSTRACT. Increasing amounts of Digoxin, Lasix@, Teofyllamin and (3-775 were added to human blood in vitro and the whole blood oxygen affinity was measured. We found no definite proof that any of the drugs was able to affect the oxygen affinity of the red cells even at unphysiologically high concentrations. Key words: cardioactive drugs, oxygen affinity, 2,3-di- phosphoglycerate, plasma pH, intraerythrocytic pH. Acta Med Scand 205: 49, 1979. It has been suggested that the oxygen affinity of blood is increased in patients with severe peripheral arteriosclerosis (3). It is also suggested that the circulating blood of diabetics, who have a tendency to develop premature arteriosclerosis, has a de- creased ability to release oxygen to the tissues (2, 9). A decrease in the affinity of hemoglobin for oxygen in these conditions would favour the un- loading of oxygen to the tissues. Interest has there- fore been focussed on drugs and their ability to lower blood oxygen affinity (I, zyxwvutsrqp 15). It would be theoretically beneficial to lower blood oxygen affin- ity in patients with angina pectoris in whom the affinity is normal or increased, as this should aug- ment oxygen availability to the tissues. Propranolol in unphysiologically high concentrations has been shown to decrease blood oxygen affinity in vitro (15). At the therapeutic concentrations encountered in vivo the bloof oxygen affinity was not affected zyxwvu (13). According to Corey and Hastings (81, (3-775, which is a cardioselective P-adrenergic blocking agent, but not propranolol or practolol, decreased the oxygen affinity of the blood at therapeutic levels. The aim of this investigation was to examine the effects in vitro of four arbitrarily chosen drugs used in the treatment of cardiovascular diseases, namely Digoxin, Lasix@, Teofyllamin, and CI-775, on oxy- gen affinity of human whole blood. MATERIAL AND METHODS Drugs Digoxin: 1 ml contains 0.25 mg digoxin, 0. I g spir. fortis, propylene glycol, citric acid, natr. phosph. et aq. steril. ad 1 ml, pH 7.1. Lasix": I ml contains 10 mg furosemide, natr. hydrox- ide normal. et natr. chloride q. s., aq. steril. ad 1 ml, pH Teofyllamin: 1 ml contains 23 mg aminophylline (re- spond. 20 mg theophylline, zyxw 5.5 mg ethylenediamine hydr.) natr. chloride et aq. steril. ad 1 ml, pH 8.8. CI-775: I ml contains 10 mg acebutolol et aq. steril. ad 1 ml, pH 5.0-5.8. Blood from 14 healthy, non-smoking male and female volunteers was used for the experiments. Blood samples were drawn twice from 6 volunteers. Each drug tested was added to 5 different blood samples and the analyses were performed within 15 min of sampling. Increasing amounts of the drugs-O.001, 0.005, 0.01, 0.02, and 0.04 ml-were added to 1 ml of blood. The lowest of these concentrations in the blood was of a magnitude that may occur in vivo using Lasix and Teofyl- larnin, while Digoxin and (3-775 were used in un- physiologically high concentrations. In order to obtain baseline values, double analyses on blood without any drug added were performed on each volunteer and the mean values of zyxw P50 stand, P50 ery, PSO act, pH pl, and pH ery were determined (for definitions see below). The technics have been described elsewhere (6). The same parameters were then measured in single analyses on blood to which increasing amounts of each drug had been added. The deviation of these parameters from the baseline value of each single individual was then calcu- lated. Carboxyhemoglobin (COHb), determined in all 8.9-9.2. Abbreviations: Hb= hemoglobin, COHb=carboxyhemo- globin, 2,3-DPG= 2,3-diphosphoglycerate, PO,=oxygen tension, PCO,=carbon dioxide tension, pH pl=plasma pH, SO,=oxygen saturation. 4-79298 I