Pine oil toxicity in the horse: drug detection, residues and pathological changes.

This report concerns the detection and acute toxicity of pine oil (a commercially available disinfectant) after intravenous administration in horses. alpha Terpineol was identified as a major constituent of pine oil. alpha Terpineol was recovered from equine tissues by extraction into heptane and detected by gas chromatography, using either flame ionization detection or pentafluoropropionic anhydride derivatization and electron capture detection. After intravenous injection of 0.1 ml/kg, death due to massive pulmonary edema occurred within minutes. In this animal blood and tissue levels of alpha-terpineol of between 150 and 300 ppm were observed. After smaller doses of pine oil (0.033 ml/kg), horses survived until euthanized up to 48 hours later. Blood levels of alpha-terpineol became undetectable in one of these animals after 2 hours, and no tissue levels were detected at postmortem. Marked histopathological changes were seen in the lungs of animals which survived the initial injection period. It appears that after intravenous injection of pine oil in horses lesions are largely related to the respiratory tract, and the mechanism of death is acute pulmonary edema.