Further studies on allopurinol‐induced hyperuricaemia and visceral gout in red‐tailed hawks (Buteo jamaicensis)

Abstract

To investigate the usefulness of allopurinol for the treatment of hyperuricemia in birds, experimental studies were performed using the physiologically occurring post-prandial hyperuricaemia in birds of prey as a model. Pre-and post-prandial plasma concentrations of allopurinol, oxypurinol, xanthine, hypoxanthine and uric acid were established by high performance liquid chromatography in red-tailed hawks (RTH, Buteo jamaicensis) at various time intervals after receiving allopurinol (50 mg/kg SID) or placebo. The dosage used caused slight, but significantly elevated plasma uric acid concentrations compared to controls, as well as vomiting in the majority of treated birds. Markedly elevated plasma concentrations of oxypurinol, xanthine and hypoxanthine were seen in experimental birds. Toxic signs were attributed to oxypurinol, the active (and toxic) metabolite of allopurinol. Xanthinuria was considered to be the cause of the observed renal function disorder. Extrapolation of data from studies in humans and combining these with those of the present study suggest that the maximum dose of allopurinol that can be safely administered to RTH is about half the dose given in the present study, but this needs verification.

Further studies on the use of allopurinol to reduce plasma uric acid concentrations in the Red-tailed Hawk ( Buteo jamaicensis ) hyperuricaemic model

“…The limit of sensitivity is 1 m mol/l. This is the same protocol used in the experiment with Red-tailed Hawks receiving 50 mg/kg allopurinol (Lumeij et al, 1998).…”

“…This indicates that oral administration of allopurinol does not prevent the occurrence of physiologic postprandial hyperuricaemia in Red-tailed Hawks. Lumeij et al (1998) further investigated the effect of allopurinol on postprandial hyperuricaemia in birds of prey and confirmed the risk of allopurinol-induced nephropathy in Red-tailed Hawks. Although the initial dosage used in this follow-up experiment (50 mg/ kg) was lower than in the previous experiment of 1992 (100 mg/kg followed by 50 mg/kg), the dosage used still induced signs of toxicity like vomiting and a renal function disorder.…”

“…Lumeij & Redig (1992) and Lumeij et al, (1998) performed controlled studies on the effect of allopurinol (dosages employed ranged from 10 to 100 mg/kg SID) using the physiological occurring postprandial hyperuricaemia in birds of prey as a model. Significant postprandial increases in plasma uric acid and plasma urea concentrations are observed in raptors.…”

“…To investigate whether a lower dose of allopurinol can be safely administered to Red-tailed Hawks at half the dose given in the study of Lumeij et al (1998) an experiment was conducted using the same protocol, administrating 25 mg allopurinol/kg SID.…”

Birds of prey anaesthesia

“…In cases of uricaemia, allopurinol may be used to decrease uric acid production, but renal toxicity has been reported in red-tailed hawks (Buteo jamicensis) receiving this drug (Lumeij et al, 1998). Carnivorous birds such as birds of prey should be fasted before blood sampling, as false-positive elevations in blood uric acid levels will be seen in birds that have not been fasted (O'Malley, 2005).…”