Serum uric acid (UA) is known to be elevated in adolescents with hypertension, but only recently have results from animal studies suggested a causal relation. Investigators performed a randomized, double-blind, placebo-controlled crossover study to determine whether lowering serum UA levels with allopurinol (200 mg twice daily for 4 weeks) reduces blood pressure (BP) in children with stage 1 hypertension (BP >95th percentile and <99th percentile + 5 mm Hg) and serum UA levels 6.0 mg/dL.

Of 30 children (age range, 11–17 years), 73% were overweight or obese. Allopurinol treatment resulted in significant reductions in serum UA concentrations, in casual systolic BP (mean reduction, 6.9 mm Hg) and diastolic BP (mean reduction, 5.1 mm Hg), and in ambulatory systolic BP (mean reduction, 6.3 mm Hg) and diastolic BP (mean reduction, 4.6 mm Hg). Placebo treatment was not associated with significant BP changes. Twenty-nine patients remained hypertensive during placebo treatment, whereas only 10 remained hypertensive during allopurinol treatment. Plasma renin levels and peripheral vascular resistance decreased significantly during treatment with allopurinol but not with placebo. No adverse effects were reported.

Comment: Serum UA levels are an important component of the evaluation of hypertension in children. UA levels often are elevated in patients with hypertension, and elevated levels have long been thought to be a marker for vascular injury resulting from prolonged hypertension. These data suggest that serum UA should be monitored in children with hypertension, and, if levels are significantly elevated, treating the UA elevation might treat the hypertension. Because obesity itself raises serum UA levels, UA elevation might be one mechanism for obesity-related hypertension.

— F. Bruder Stapleton, MD

Published in Journal Watch Pediatrics and Adolescent Medicine September 3, 2008