Presumptive renal tubular acidosis secondary to topiramate administration in a cat

Abstract

Objective: To describe renal tubular acidosis (RTA) and secondary acquired hyperaldosteronism in a cat as an adverse effect of topiramate therapy.Case Summary: An 8-year-old neutered female cat on chronic oral topiramate therapy at a recommended dose (11.9 mg/kg q 8 h) for seizure control was presented with severe metabolic acidosis and hypokalemia. Plasma electrolyte and acid-base analysis identified a severe metabolic acidosis (pH 7.153, reference interval: 7.31-7.46), hypokalemia (2.08 mmol/L [2.08 mEq/L], reference interval: 3.5-4.8 mmol/L [3.5-4.8 mEq/L]), and ionized hypercalcemia (1.85 mmol/L [1.85 mEq/L], reference range: 1.1-1.4 mmol/L [1.1-1.4 mEq/L]). Urinalysis revealed a urine specific gravity of 1.021 and a pH of 7.0. Diagnostic workup suggested distal RTA as a cause of the cat's acid-base and electrolyte disturbances. Aldosterone concentration was moderately increased, suggestive of secondary hyperaldosteronism. The metabolic abnormalities resolved with supportive care and discontinuation of topiramate.

A review of renal tubular acidosis

“…10,267,[286][287][288][289]291 Hypokalemia is commonly reported in cats with dRTA and is often severe. 266,285,286 Inappropriately alkaline urine during acidemia confirmed dRTA in several case reports. 285,286,291,305 3.2.2 Proximal (type 2) RTA Common clinical signs observed in cases of pRTA include polyuria, polydipsia, dehydration, vomiting, anorexia, and weight loss.…”

“…266,285,286 Inappropriately alkaline urine during acidemia confirmed dRTA in several case reports. 285,286,291,305 3.2.2 Proximal (type 2) RTA Common clinical signs observed in cases of pRTA include polyuria, polydipsia, dehydration, vomiting, anorexia, and weight loss. 12,268,277,278,295,297,302,303 As reports of pRTA in dogs mainly involve cases of Fanconi syndrome, laboratory abnormalities commonly include persistent paradoxical glucosuria, bicarbonaturia, defective tubular reabsorption of sodium, potassium and uric acid, ketonuria, hyperphosphaturia leading to hypophosphatemia, aminoaciduria, and tubular proteinuria.…”

“…Topiramate was considered a probable cause for the dRTA because of rapid resolution after its discontinuation. 285 The topical CAI dorzolamide has been associated with dRTA in a cat who presented with signs of hypokalemia and laboratory abnormalities consistent with dRTA. 286 The RTA and hypokalemia resolved with discontinuation of the dorzolamide, short-term supportive care, and potassium supplementation.…”

“…9 Distal RTA was presumed in an 8-year-old domestic shorthair cat treated with topiramate for seizures related to a left piriform lobe mass. 285 Venous blood gases at the time of initial diagnosis were normal. Four months after starting topiramate concurrently with other anticonvulsants for uncontrolled seizures, the cat was diagnosed with dRTA based on metabolic acidosis, hypokalemia, and a high urine pH.…”

“…CAIs, including the antiepileptic drugs zonisamide and topiramate and the topical CAI dorzolamide, have been reported as causative agents of RTA. 9,285,286 Zonisamide therapy was implicated in causing dRTA in a male Schipperke but resolved with discontinuation of the drug. 9 In February 2009, the Food and Drug Administration issued a warning that zonisamide can cause metabolic acidosis in people and recommended monitoring of serum HCO 3 , even in asymptomatic individuals.…”