PMID: 6103939Mar 1, 1980Paper

In vitro and in vivo alpha-blocking activity of thymoxamine and its two metabolites

The Journal of Pharmacy and Pharmacology
M H CreuzetJ Roquebert

Abstract

The alpha-adrenoceptor potency of thymoxamine and its two metabolites deacetylthymoxamine and demethyldeacetylthymoxamine were determined on the contraction of rat vas deferens induced by noradrenaline, the blood pressure increase induced by noradrenaline given i.v. to dogs and the contraction of the nictitating membrane induced by electrical stimulation in cats. In vivo the three drugs were administered at 6.35 x 10(-6) mol kg-1 intravenously. Deacetylthymoxamine presented nearly the same alpha-blocking activity as the parent drug. This was ascribed in vivo to the rapid deacetylation of thymoxamine. Demethyldeacetylthymoxamine was less active. In vitro its pA2 was 6.20 +/- 0.09 compared with 6.75 +/- 0.20 for thymoxamine and 6.57 +/- 0.13 for deacetylthymoxamine. In vivo, it was inactive in dog and less active than the other two drugs soon after its administration in the cat. The oral LD 50 values in the mouse for the three drugs were respectively 0.81, 0.71 and 1.14 mmol kg-1 for thymoxamine, deacetylthymoxamine and demethyldeacetylthymoxamine.

References

Feb 1, 1976·British Journal of Pharmacology·A Jurkiewicz, N H Jurkiewicz
Jul 1, 1977·European Journal of Pharmacology·J M van NuetenP A Janssen
Feb 1, 1980·The Journal of Pharmacy and Pharmacology·C FeniouJ Roquebert

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Citations

Jan 1, 1985·European Journal of Drug Metabolism and Pharmacokinetics·K O VollmerW Steinbrecher
Dec 1, 1992·Journal of Pharmaceutical Sciences·P CostaB Sarrazin
Feb 1, 1980·The Journal of Pharmacy and Pharmacology·C FeniouJ Roquebert
Sep 1, 1993·Journal of Pharmaceutical Sciences·P CostaM Galtier

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