title: Tolerance to sympathomimetic bronchodilators in guinea-pig isolated lungs following chronic administration in vivo.
abstract: 1 Pretreatment of the guinea-pig subcataneously three times daily with either 5 mug/kg isoprenaline or adrenaline reduced the response of the isolated perfused histamine-constricted lung when challenged with either the same or a different sympathomimetic bronchodilator. The longer the animals were pretreated and the higher the dose of bronchodilator the greater was the degree of tolerance developed. 2 Tolerance was developed to aminophline in the same preparation when the guinea-pig had been pretreated with aminophyline or isoprenaline. Cross-tolerance also developed adrenaline when the guinea-pig had been pretreated with aminophyline. 3 Tolerance was still persistent in guinea-pigs one and two weeks after pretreatment three times daily with either isoprenaline of adrenaline (5 mu/kg s.c.) for seven days in the same preparation. Only after three weeks was the tolerance diminished. 4 These results suggest that asthmatic patients who use bronchodilators excessively may become refractory to the bronchodilator effect of these drugs. They also support the hypothesis that induced cross-resistance to endogenous sympathetic stimulation could lead to a deterioration of the asthmatic state in patients using the sympathomimetic bronchodilators and that this may explain the increase in asthma mortality rate. 5 A mechanism of tolerance to sympathomimetic bronchodilators is postulated.
mesh_terms: D000403:Airway Resistance / Q000187:drug effects; D000628:Aminophylline / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001993:Bronchodilator Agents / Q000494:pharmacology*; D004361:Drug Tolerance; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000187:drug effects*; D008297:Male; D013566:Sympathomimetics / Q000494:pharmacology*; D013726:Terbutaline / Q000494:pharmacology; D013997:Time Factors
chemical_list: D001993:Bronchodilator Agents; D013566:Sympathomimetics; D000628:Aminophylline; D006632:Histamine; D007545:Isoproterenol; D013726:Terbutaline; D001205:Ascorbic Acid; D004837:Epinephrine