[Effects of oxyfedrine on sinus nodal function and AV-conduction (author's transl)]

In 20 patients the electrophysiologic effects of oxyfedrine at doses of 0.3 mg/kg/hr and 0.6 mg/kg/hr were studied. At the low dose, oxyfedrine caused a significant shortening of the absolute and rate-corrected sinus node recovery time by 16 and 27 percent, respectively. Sinus cycle length decreased slightly by 9 percent. Estimated sinoatrial conduction time tended to shorten, but not significantly so. AV-nodal conduction was slightly accelerated at sinus rhythm as well as during atrial stimulation; correspondingly paced cycle length at which Wenckebach AH-conduction occurred decreased. HV-interval remained unchanged. Increasing the dose of oxyfedrine had no additional effect on electrophysiologic parameters compared to the first dose used. The results demonstrate a moderate stimulatory action of oxyfedrine on sinus nodal automaticity and a slight acceleration of AV-nodal conduction. Whether the drug might be useful in the clinical setting for medical management of sinus nodal dysfunction or AV-conduction disturbances, remains to be elucidated on long-term studies; more pronounced effects of oxyfedrine than found in this investigation, however, are expected to be limited by its autoinhibitory action at higher dose levels.