Therapeutics of hyperuricaemia and gout

The influence of allopurinol on urinary purine loss after repeated sprint exercise in man

The influence of allopurinol on urinary purine loss was examined in 7 active male subjects (age 24.9 +/- 3.0 years, weight 82.8 +/- 8.3 kg, V O2peak 48.1 +/- 6.9 mL.kg(-1).min(-1)). These subjects performed, in random order, a trial with 5 days of prior ingestion of a placebo or allopurinol. Each trial consisted of eight 10-second sprints on an air-braked cycle ergometer and was separated by at least a week. A rest period of 50 seconds separated each repeated sprint. Forearm venous plasma inosine, hypoxanthine (Hx) and uric acid concentrations were measured at rest and during 120 minutes of recovery from exercise. Urinary inosine, Hx, xanthine, and uric acid excretion were also measured before and for 24 hours after exercise. During the first 120 minutes of recovery, plasma Hx concentrations, as well as the urinary Hx and xanthine excretion rates, were higher (P < .05) with allopurinol compared with the placebo trial. In contrast, plasma uric acid concentration and urinary uric acid excretion rates were lower (P < .05) with allopurinol. The total urinary excretion of purines (inosine + Hx + xanthine + uric acid) above basal levels was higher in the allopurinol trial compared with placebo. These results indicate that the total urinary purine excretion after intermittent sprint exercise was enhanced with allopurinol treatment. Furthermore, the composition of urinary purines was markedly affected by this drug.

Allopurinol blocks shock-wave-induced rises in cytosolic calcium levels in MDCK cells

Allopurinol has been reported to ameliorate the side effects in patients following shock wave lithotripsy (SWL); however, the mechanism has not been studied. We have examined the protective effect of allopurinol on Madin-Darby canine kidney (MDCK) cells after shock wave exposure (SWE) by determining the release of aspartate aminotransferase (ASAT) and lactate dehydrogenase (LD), and the resting cytosolic Ca2+ concentration ([Ca2+]i). In SWE-treated cells, the release of ASAT and LD increased immediately, but largely transiently, by approximately 23% and 5-fold over control, respectively. Within 1-6 h after SWE there was a gradual rise in the resting [Ca2+]i of 16-137% above control. Allopurinol did not affect the transient enzyme release but blocked the long-term rises in the resting [Ca2+]i. The transient changes in [Ca2+]i evoked by two hormones, ATP and bradykinin, and a drug that releases Ca2+ from internal Ca2+ stores, thapsigargin, were only slightly affected in allopurinol-treated cells. We conclude that the protection conferred by allopurinol on patients treated with SWL might involve a direct protection of the kidney cells by maintaining a normal resting [Ca2+]i.

Drug-induced rheumatic syndromes. Diagnosis, clinical features and management

In order to avoid inappropriate therapy and prolonged morbidity, it is important to recognise when a patient's rheumatic complaints are due to drugs. However, this is often difficult because of the large number of drugs that have been implicated and the diversity of clinical presentations. Arthropathy may be seen with several different syndromes, including drug-induced lupus erythematosus (DILE), serum sickness and gout. The most widely reported of these is DILE, which usually develops after some months or even years of drug therapy. While many authors do not specifically require their presence for the diagnosis of DILE, antinuclear antibodies have been detected in the great majority of reported patients with DILE, whatever the causative drug. In contrast, patients who develop arthropathy soon after commencing a drug rarely have antinuclear antibodies and appear to be distinct from patients with DILE. Apart from arthropathy, a number of other syndromes that appear to have an immunological basis may be induced by drugs. Cutaneous vasculitis is not uncommon and drugs are frequently considered to be the aetiological factor. Whether drugs may cause larger vessel systemic vasculitis is less certain. Rarely, polymyositis and scleroderma-like syndromes have been associated with drug therapy. Corticosteroid-induced osteoporosis is a complication of all the corticosteroid preparations that are widely used at present. However, the development of deflazacort, a so-called 'bone-sparing' steroid, has raised the possibility that the effect of corticosteroids on bone may be separable, at least in part, from the other actions of these drugs. Data have been conflicting with regard to whether there is a 'safe' dose of corticosteroid. Similarly, it is unclear whether prophylactic therapy with agents such as calcium, fluoride and vitamin D is beneficial. Nonetheless, recent findings suggest that approaches will be developed to minimise the risk of osteoporosis in patients who require corticosteroids. There are a number of other ways in which drugs may affect bones. Osteomalacia is a well-known but uncommon complication of treatment with anticonvulsants and occasionally other drugs. The mechanism probably relates to the induction of hepatic enzymes and the consequent increased metabolism of vitamin D in patients with borderline levels initially. Osteosclerosis may also result from drug therapy; usually with fluoride or retinol (vitamin A) and its analogues. With continued research, the true spectrum of drug-induced rheumatic syndromes should become more clearly defined.(ABSTRACT TRUNCATED AT 400 WORDS)