Supra‐Additive Interaction of Docosahexaenoic Acid and Naproxen and Gastric Safety on the Formalin Test in Rats

ABSTRACT Preclinical Research The aim of this work was to evaluate the effect of docosahexaenoic acid (DHA) on the pharmacokinetics and pharmacodynamics—nociception—of naproxen in rats, as well as to determine the gastric safety resulting from this combination versus naproxen alone. Female Wistar rats were orally administered DHA, naproxen or the DHA‐naproxen mixture at fixed‐ratio combination of 1:3. The antinociceptive effect was evaluated using the formalin test. The gastric injury was determined 3 h after naproxen administration. An isobolographic analysis was performed to characterize the antinociceptive interaction between DHA and naproxen. To determine the possibility of pharmacokinetic interactions, the oral bioavailability of naproxen was evaluated in presence and absence of oral DHA. The experimental effective dose ED30 values (Zexp) were decreased from theoretical additive dose values (Zadd; P