Studies on the action and mechanism of action of oxyfedrine on isolated tracheal chains

Oxyfedrine, a β-sympathomimetic drug, did not affect isolated rat and rabbit trachea in concentration from 2.86 × 10^?8 to 2.86 × 10^?4 M, but on the guinea-pig trachea, it caused a dose dependent relaxation of natural tone in lower concentrations (1.79 × 10^?7 to 2.86 × 10^?6 M. In higher concentrations (1.14 × 10^?5 to 2.86 × 10^?4 M), however, a contraction was observed, which was also dose dependent. This contraction was not affected by atropine, lysergic acid diethylamide or by pretreatment with reserpine but was blocked by antihistaminics (isothipendyl and clemastine). Adrenaline, noradrenaline, phenylephrine and isoprenaline did not contract the guinea-pig trachea, whereas contractions were observed after high concentrations of norephedrine, amphetamine, ephedrine and tyramine. These contractions were also unaffected by reserpine pretreatment.It is concluded that the contraction of the guinea-pig trachea by oxyfedrine is related to its structural relationship to the phenylethylamines and might be due to histamine release, an action on histamine receptors or a histamine-like action.