Pain relief for koalas: a study on acetaminophen use

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Koalas are accident prone marsupials. Many of them are free-range, which puts them at risk of getting injured by cars, forest fires, and animal attacks.¹ Past investigators have tried many different options to help them in their healing process including the use of fentanyl, meloxicam, and tramadol.¹

A group of investigators in Australia recently studied the use of acetaminophen oral tablets—known as paracetamol in some parts of the world—in the koala population. Although acetaminophen and codeine have been given orally to koalas for many years, analysis of the actual kinetics of acetaminophen by itself in koalas was limited.

Koalas stand at about 2 to 3 feet tall and can weight anywhere from 4 kg to 13 kg (9-29 lbs.)² The investigators administered an oral dose of 15 mg/kg twice daily to 8 adult koalas at the Taronga Zoo in New South Wales, and then looked for any significant changes in the koala’s hematology, plasma electrolytes, and biochemical analytes. The investigators then chose a dose of 15mg/kg based on previous recommendations in a commonly used textbook in Australia.¹

Acetaminophen has been found to be toxic in many other animal species such as cats and dogs because their metabolisms break the drug down into toxic metabolites. However, according to the results of this recent study, koalas possess the necessary enzymes for acetaminophen to be ingested and metabolized safely.¹

The studied dose of 15 mg/kg given twice daily reached the therapeutic plasma concentration necessary to provide mild to moderate pain relief in humans but may not be the answer for koalas. The researchers found lower quantities of active drug in the koala’s systems because of protein binding, which means the chosen dosing range may need to be increased for koalas to feel the same benefits from the drug as humans.¹

RELATED NEWS: Study analyzes severity of injuries found in koalas affected by Australian bushfire

Christina Nault is a 2025 PharmD candidate and veterinary pharmacy student at the University of Connecticut in Storrs.

References

1. Govendir M, Vogelnest L, Shapiro AJ, Marschner C, Kimble B. Pharmacokinetic profile of oral and subcutaneous administration of paracetamol in the koala (Phascolarctos cinereus) and prediction of its analgesic efficacy. PLoS ONE. April 17, 2024. Accessed August 9, 2024. https://doi.org/10.1371/journal.pone.0300703
2. 2.Nature. Koala Fact Sheet. PBS. July 1, 2020. Accessed August 9, 2024. https://www.pbs.org/wnet/nature/blog/koala-fact-sheet/#:~:text=Size%20and%20Weight%3A