Situs inversus totalis and lung cancer.

Communications to the Editor local vasodilator and reduces platelet aggregation in vitro; it is believed to mediate dipyridamole’s in moo antiplatelet and vasodilator effects. It is unclear how methylxanthines cause bronchodilation; almost all act to block adenosine receptors. Aminophylline has been shown to reduce cerebral blood flow, probably by antagonizing the vasodilator effects of adenosine. I am concerned that, when dipyridamole is used as an antithrombotic agent, simultaneous use of methybcanthines (either therapeutically or in the diet) will inhibit the desired effects. Clinically, IV aminophylline is used as the antidote for the coronary vasodilatory effects ofIV dipyridamole in dipyridamole-Thallium cardiac studies. Caffeine antagonizes adenosine effects in humans. Theophylline will block hemodynamic effects ofdipyridamole related to elevated plasma adenosine levels. It has recently been questioned in several multicenter studies as to whether the combination of aspirin and dipyridamole has more effectiveness as an antithrombotic agent than aspirin alone.6 These studies did not look at use of medical or dietary methylxanthines. It would be of interest to study the antithrombotic effects of dipyridamole in patients who are not receiving methylxanthines. For now, it would be prudent to avoid the use of methybcanthines in patients taking dipyridamole.