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Dose‐dependent plasma elimination of subcutaneously administered calcium heparin in horses
Author(s) -
GERHARDS H.,
KIETZMANN M.
Publication year - 1988
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.1988.tb00124.x
Subject(s) - heparin , chemistry , subcutaneous injection , pharmacokinetics , calcium , body weight , zoology , medicine , pharmacology , biochemistry , biology
Gerhards, H., & Kietzmann, M. Dose‐dependent plasma elimination of subcutaneously administered calcium heparin in horses. J. vet. Pharmacol. Therap. 11 , 77–83. Pharmacokinetic parameters for subcutaneous low dose heparin in horses have been determined. Four groups of five and one group of eleven mature, healthy horses of various breeds were given single subcutaneous injections of 60, 80, 100, 125, and 150 units of calcium heparin/kg of body weight (U/kg) in the pectoral region. Jugular blood samples were collected prior to, and at hourly intervals for 12 h after injection. Heparin plasma concentrations were measured using a commercially available amidolytic assay. Peak concentrations 4 h after administration were 0.021 ± 0.016 (mean ± SD) units of heparin/ml of plasma (U/ml) after 60 U/kg, 0.035 ± 0.025 U/ml after 80 U/kg, 0.023 ± 0.004 U/ml after 100 U/kg, 0.034 ±0.019 U/ml after 125 U/kg, and 0.053 ±0.019 U/ml after 150 U/kg. Data from groups given 60 and 100 U/kg could not be used for kinetic calculations. Elimination constant (1/h), elimination half‐life (h), and elimination time (h) calculated to reach base‐line values after 80 U/kg were 0.182 ± 0.041 1/h, 3.8 ± 0.9 h, and 9.7 + 2.2 h. After 125 U/kg, corresponding values were 0.211 ± 0.019 1/h, 3.3 ± 0.3 h, 13.4 ± 1.2 h, and after 150 U/kg 0.098 ± 0.015 1/h, 7.1 ± 1.1 h, and 20.6 ± 3.2 h. Calculated heparin concentrations 12 h after administration of 80, 125, and 150 U/kg were 0.011 ± 0.002, 0.010 ± 0.001, and 0.027 ± 0.004 U/ml. After seven successive injections of 150 U/kg at 12 h intervals in one horse, the elimination constant decreased from 0.23/h after the first to 0.08/h after the seventh injection, and the elimination time increased from 10 h to 40 h. Reducing the dosage from 150 U/kg initially to 125 U/kg for six successive injections reduced the prolonged elimination after repeated injections.