Aspirin : Rheumatic Fever in Obese Patient

• No sufficient information on the pharmacodynamics in obese patients
• Based on a single dose study, distribution of salicylate into that fraction of body weight which is in excess of ideal weight-presumed to consist mainly of adipose tissue is proportionately less than its distribution into ideal weight.
• This is consistent with the physicochemical profile of salicylate that demonstrates its relatively nonlipophilic character
• Apparent clearance of salicylate, likewise, was minimally influenced by obesity
• However, peak salicylate concentrations averaged 26% lower in the obese volunteers due to their larger v d . Since the efficacy of aspirin following single doses for the acute treatment of pain or inflammation probably is related to the peak serum concentration, the findings suggest that obese individuals require higher doses in these circumstances

Dosing Recommendations

• No specifc guides for obese/overweight patients
• typical doses of aspirin used to reduce fever and alleviate arthritis symptoms are
• 80 to 100 mg/kg per day in divided doses every four hours in [children]
• 4 to 8 g/day in adults in divided doses every four to six hours.
• However, many experts recommend starting at a lower dose of 50 to 60 mg/kg/day in children because of the risks of salicylate toxicity characterized by tinnitus, headache, and tachypnea

References:

• INFLUENCE OF AGE, GENDER, AND OBESITY ON SALICYLATE KINETICS FOLLOWING SINGLE DOSES OF ASPIRIN. Arthritis and Rheumatism, Vol. 29, NO. 8 (August 1986)
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