Adenosine is worth trying in patients with paroxysmal supraventricular tachycardia on chronic theophylline medication.

Adenosine is widely used to terminate paroxysmal supraventricular tachycardia. However, it is usually considered of no value in patients on theophylline, for methylxanthines completely antagonize the A(1) -receptor mediated negative dromotropic adenosine effect. We report a case of a 69 year old man who had chronic obstructive lung disease and spontaneous pneumothorax. Supraventricular tachycardia with a heart rate of 200 bpm persisted even after a pleural drain was inserted and the lung became fully inflated. Although the patient was on theophylline medication with effective serum plasma levels, adenosine terminated the supraventricular tachycardia after three repeated doses of 3, 6 and 9 mg, respectively. This observation further nourishes previous hypotheses that chronic administration of an A1-receptor antagonist leads to up-regulation of the adenosine receptor number.