Effects of the new antiallergic drug 11-oxo-11H-pyrido[2,1-b] quinazoline-2-carboxylic acid on bronchial and cutaneous allergic responses to ascaris in dogs.

The effects of 11-oxo-11H-pyrido[2,1-b]quinazoline-2-carboxylic acid (Sm 857), a new antiallergic drug, on both bronchial asthma and active cutaneous anaphylaxis (ACA) reaction induced by Ascaris suum antigen in dogs were investigated. The airway resistance was determined using the modified Konzett-Rössler method. Sm 857 in doses of 30 and 100 mg/kg intraduodenally (i.d.) produced a remarkable inhibitory effect on the asthmatic bronchoconstriction induced by inhalation of Ascaris antigen in naturally sensitized dogs. Intravenous administration of Sm 857 (10 mg/kg) also strongly inhibited the Ascaris-induced bronchial asthma. Sm 857 had a more powerful antiasthmatic activity than tranilast. In ACA reactions, 10 dilutions of Ascaris extract and histamine were injected intradermally to dogs and each wheal provoked was determined. Sm 857 (100 and 300 mg/kg i.d.) had little or no inhibitory effect on the antigen-induced wheals, while tranilast only in a high dose (300 mg/kg i.d.) showed an inhibitory effect. Chlorpheniramine (10 mg/kg i.d.) prevented the ACA reaction completely. Sm 857 thus appeared to have no antihistaminic effect. Above findings suggest that Sm 857 may be useful for the treatment of bronchial asthma as an orally active drug, exerting its action probably through a mast cell stabilizing effect.