Pharmacokinetics of glaucine after intravenous and oral administrations and detection of systemic aporphine alkaloids after ingestion of tulip poplar shavings in horses

Glaucine, an aporphine alkaloid with anti‐tussive, anti‐inflammatory, and anti‐nociceptive properties, has been identified in post‐race samples from racehorses. To investigate pharmacokinetics of glaucine in horses, a three‐way crossover study of intravenous and oral glaucine (0.1 mg/kg) and orally administered tulip poplar shavings (50 g shavings = 0.001 mg/kg glaucine) was performed in six horses. A two‐compartment model best described IV administration with alpha (t1/2α) and beta (t1/2β) half‐life lives of 0.3 (0.1–0.7) and 3.1 (2.4–7.8) h, respectively. The area under the curve (AUC0∞iv) was 45.4 (34.7–52.3) h*ng/ml, and the volume of distribution of the central (Vdc) and peripheral (Vdp) compartments was 2.7 (1.3–4.6) and 4.9 (4.3–8.2) L/kg, respectively. A one compartment model best described the oral administration of glaucine with absorption (t1/2ka) and elimination (t1/2kel) half‐lives of 0.09 (0.05–0.15) and 0.7 (0.6–0.8) h, respectively. The area under the curve (AUC0∞PO) was 15.1 (8.0–19.5) h·ng/ml. Bioavailability following oral administration was 17%–48%. Following ingestion of shavings, glaucine and liriodenine were detectable in plasma for up to 16 and 48 h, respectively. Glaucine was quantifiable briefly in the urine from two horses. Liriodenine was quantifiable in urine for 12–20 h in four horses and for 48 h in two horses. The presence of liriodenine indicates ingestion of tulip poplar tree parts, however, does not rule out co‐administration of purified glaucine in horses.