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Case Reports
. 2022 Nov;8(6):2256-2260.
doi: 10.1002/vms3.905. Epub 2022 Aug 2.

Distal renal tubular acidosis and lethargy associated with zonisamide treatment in a dog with idiopathic epilepsy

Takamasa Itoi  1   2 , Natsuki Akashi  1   2 , Yuki Shimizu  1 , Keisuke Sugimoto  1   2 , Akihisa Hata  2 , Kenji Kutara  1   2 , Takako Shimokawa Miyama  1   2 , Teppei Kanda  1   2
Affiliations
Case Reports

Distal renal tubular acidosis and lethargy associated with zonisamide treatment in a dog with idiopathic epilepsy

Takamasa Itoi et al. Vet Med Sci. 2022 Nov.

Abstract

A 3-year-old neutered male golden retriever administered zonisamide for the treatment of seizures showed lethargy and had normal anion gap metabolic acidosis with hypokalaemia, hyperchloremia, and alkaline urine. The serum zonisamide concentration was close to the upper limit, which raised a suspicion of adverse effects of zonisamide. This is the first report showing that the fractional excretion of bicarbonate after compensation for the plasma bicarbonate concentration by a sodium bicarbonate infusion was approximately 5%, indicating distal renal tubular acidosis (RTA). The serum zonisamide concentration decreased, and adverse effects were abated by reducing the zonisamide dosage. Diagnostic therapy with bicarbonate served as a means of compensating for bicarbonate deficiency and contributed to the clinical diagnosis of the condition in zonisamide-associated RTA in dogs.

Keywords: bicarbonate; dog; fractional excretion; renal tubular acidosis; zonisamide.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Venous blood bicarbonate concentrations and urine fractional excretion (FE) of bicarbonate before (baseline) and during a bicarbonate loading test with sodium bicarbonate infusion at 0.5, 1.0, and 2.0 mEq/kg/h in a dog with renal tubular acidosis attributed to zonisamide treatment.
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