d,l-Methionine in combination with amoxicillin-clavulanic acid successfully dissolves spontaneously occurring infection-induced struvite urocystoliths in dogs: a pilot study

OBJECTIVE To determine the efficacy and safety of a urinary acidifier (d,l-methionine [Methio-Form]) and an antimicrobial agent (amoxicillin-clavulanic acid [Clavamox]) without changing diet for dissolving infection-induced struvite urocystoliths in dogs. ANIMALS 14 dogs were recruited for this prospective study; 11 completed it and 3 dogs withdrew due to inability of the owners to administer the treatment (n = 2) or refusal of treatment by the dog (1). PROCEDURES All dogs were administered d,l-methionine (approx initial dose of 75 mg/kg, PO, q 12 h) and amoxicillin-clavulanic acid (22 mg/kg, PO, q 12 h) based on urine culture and sensitivity. Urine pH, urinalysis, urine culture, venous blood gas and serum biochemical analysis, and lateral survey abdominal radiographic images were evaluated initially and every 4 weeks until urolith dissolution (success) or lack of change in size and/or shape of urocystoliths on 2 consecutive reevaluation points (failure) occurred. RESULTS Uroliths dissolved in 8 of 11 dogs in a median of 2 months (range, 1 to 4 months) with a final effective dosage of d,l-methionine of approximately 100 mg/kg, PO, every 12 hours. In 3 dogs, uroliths failed to dissolve and were removed surgically; they contained variable amounts of calcium oxalate. No adverse events occurred. CLINICAL RELEVANCE Infection-induced struvite urolithiasis is 1 of the 2 most common minerals occurring in canine uroliths. Results of this study supported the use of d,l-methionine and amoxicillin-clavulanic acid without changing diet for dissolution of infection-induced struvite urocystoliths in dogs.