Intramuscular tranexamic acid results in lower peak plasma concentrations but comparable systemic absorption to intravenous administration in healthy dogs.

IM tranexamic acid achieves comparable systemic exposure to IV but slower peak concentrations, supporting prehospital use when IV access is unavailable.

This pharmacokinetic study evaluated intramuscular (IM) versus intravenous (IV) administration of tranexamic acid (TXA) at 20 mg/kg in six healthy client-owned dogs using a randomized crossover design with a 6-week washout period. Plasma TXA concentrations were quantified via LC-MS/MS from baseline through 8 hours post-injection. IV administration produced a significantly higher peak plasma concentration (Cmax: 119.8 ± 17.6 μg/mL) compared to IM administration (Cmax: 46.8 ± 26.6 μg/mL), with IM Cmax reaching only approximately 39% of IV Cmax. However, IM TXA demonstrated a bioavailability of 120.9%, exceeding IV exposure in terms of total area under the curve (173.8 vs. 143.3 μg/mL·h), indicating sustained systemic absorption over a longer duration. The time to Cmax for IM administration was 1.6 ± 1.4 hours, and the half-life was approximately 33% longer than IV (2.8 vs. 2.1 hours), consistent with slower, more prolonged absorption kinetics. These findings suggest that while IM TXA does not replicate the rapid peak concentrations of IV administration—potentially limiting its utility in acute hemorrhagic emergencies—it offers comparable systemic drug exposure. This makes IM TXA a viable option in prehospital or field settings where IV access is unavailable or delayed. The authors caution that further clinical studies are required before formal IM dosing recommendations can be established for veterinary patients.

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