A comparison of the bronchodilator activity of (+/-) 11-deoxy prostaglandin E1 with its 15-methyl analogue, (doxaprost).

The bronchodilator activity of (+/-) 11-deoxy prostaglandin E1 was compared to the activity of its (+/-) 15-methyl analogue, (doxaprost). Both compounds inhibited histamine-induced bronchoconstriction in the anesthetized guinea pig where changes in tracheal pressure were measured. Doxaprost was 73 and 32 times more potent that (+/-) 11-deoxy PGE1 by the aerosol and i.v. routes, respectively. Doxaprost also demonstrated a longer duration of effect. Both compounds decreased pulmonary resistance in the 5HT tonal cat. There was no difference in the potency of the two compounds. However, doxaprost had a longer duration of effect. Both compounds caused a fall in mean arterial blood pressure after i.v. administration in the guinea pig but not after aerosol administration in the guinea pig and cat. Both compounds caused relaxation of the isolated guinea pig tracheal strip when tone was induced with carbachol. There was no difference in the potency of the two compounds. The increased activity in vivo but not in vitro of the 15-methyl analogue doxaprost is consistent with a lack of enzyme inactivation.