Background: Analgesic data in ruminant species is severely lacking. Effective dose ranges and routes of administration must be established to enable evidence-based use and improve animal welfare.
Hypothesis/
Objectives: Ha: Subcutaneous (SQ) administration of butorphanol tartrate in dairy cows achieves measurable plasma levels that are sufficiently rapid and sufficiently high to justify its clinical use when compared to intravenous (IV) administration.
Animals: 4 healthy adult Holstein cows with no recent history of medical treatment and drug administration.
Methods: Anticoagulated (K⁺EDTA) whole blood samples were collected after dosing butorphanol at 0.05mg/kg and 0.1mg/kg both intravenously and subcutaneously. Plasma samples were analyzed by reverse phase mass spectrometry. At each sample collection, vital parameter, rumen contraction and sedation level information were recorded. Feeding and rumination collar data were recorded throughout hospitalization. All data was stored in Microsoft Excel. Pharmacokinetic data was analyzed in PKSolver. Tmax, Cmax, mean concentration, absorption half-life, peak plasma concentrations and bioavailability were evaluated.
Results: No patients experienced adverse drug reactions. One patient became too sedated to stand at both 0.1mg/kg doses. SQ and IV administration at 0.05mg/kg yielded Cmax means of 2.3 µg/L and 98.32 µg/L, respectively. Administration at 0.1mg/kg yielded Cmax means of 18.75 µg/kg and 214.22 µg/kg for the SQ and IV routes, respectively.
Conclusions: Peak butorphanol concentrations are significantly lower after SQ vs IV administration. Further work is needed to determine the level of analgesia provided at these doses and subsequently their suitability for clinical use.
