Coronary dilatory action of adenosine analogues: a comparative study.

The coronary dilatory action of 23 adenosine analogues was investigated on a comparative basis after i.v. administration in anaesthetized dogs. Substitution of adenosine in position 5' with a COOH group and esterification led to a 50- to 100-fold increase in coronary efficacy (flow increase integrated over the time of action). Amidation of the carboxylic acid analogue further enhanced the coronary efficacy. The most effective analogue, adenosine-5'-ethyl-carboxamide, showed 20000 times greater activity than adenosine. Additional substitution in positions 2' and 3' with NO2, O-methoxy-methyliden or O-methoxyethyliden resulted in a delayed onset and prolonged duration of action.