These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Direct effects of H2-receptor antagonists on airway smooth muscle and on responses mediated by H1- and H2-receptors.
    Author: Koga Y, Iwatsuki N, Hashimoto Y.
    Journal: Anesthesiology; 1987 Feb; 66(2):181-5. PubMed ID: 2880532.
    Abstract:
    Because it has been suggested that histamine H2-receptor antagonists may worsen airway constriction in asthmatic patients, we investigated the comparative effects of three histamine H2-receptor antagonists on guinea pig tracheal smooth muscle in vitro. When tested against resting tone, cimetidine, ranitidine and famotidine produced dose-related relaxation with pD2 values (negative log of ED50 for relaxation) (+/- SE, n; eq 5) of 3.20 +/- 0.04, 2.95 +/- 0.16 and 2.97 +/- 0.14, respectively. Concentrations that were below threshold for relaxation, did not elicit contraction. However, when the preparations were precontracted with histamine (10(-5)M), dose-response curves for relaxation were shifted to the right, and low-concentrations of all three histamine H2-antagonists augmented histamine-induced tone. When preparations were pretreated with cimetidine (10(-6) to 10(-4) M) and then tested for sensitivity to histamine, dose-response curves for histamine-induced contraction were shifted to the left (potentiated). These results provide further evidence for a modulatory effect of airway H2-receptors on the contractile response to histamine. In addition, since the concentrations associated with potentiation of histamine-induced contraction were about the same for all three H2-receptor antagonists (greater than or equal to 10(-5) M), our studies suggest a greater likelihood of airway constriction for the less potent H2-receptor antagonists that must be administered in higher clinical doses.
    [Abstract] [Full Text] [Related] [New Search]