The effects and metabolic fate of nitroflurbiprofen in healthy volunteers

Objective: Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) are a new class of cyclooxygenase (COX) inhibitors. To investigate whether these drugs actually release nitric oxide (NO), we labeled the nitroxy group of nitroflurbiprofen with nitrogen 15 to determine the metabolic fate of this compound in humans. Method: Six healthy volunteers who fasted were given an oral dose of (15)N-nitroflurbiprofen (100 mg). Samples of blood, urine, and gastric headspace gas were taken over a 24-hour period to determine the levels of nitroflurbiprofen, flurbiprofen, total nitrate/nitrite, (15)N-nitrate/nitrite, COX activity, and gastric NO. In a crossover study (1 week apart), a further 6 healthy volunteers who fasted were given an oral dose of nitroflurbiprofen (100 mg) or flurbiprofen (65 mg) and levels of gastric NO were determined. Results. Nitroflurbiprofen was undetectable in the systemic circulation. Levels of (15)N-nitrate/nitrite (5.2% +/- 1.5% enrichment) and flurbiprofen (2.4 +/- 0.7 mug/mL) peaked at 4 hours in the plasma and gradually decreased thereafter. In unstimulated blood, the plasma levels of thromboxane B(2) (COX-1 activity) were 2 to 3 ng/mL, and after calcium ionophore stimulation, large amounts of thromboxane B, were produced (112 +/- 31 ng/mL). Prostaglandin E(2) was undetectable in unstimulated blood. After lipopolysaccharide stimulation, tion, the plasma levels of prostaglandin E, increased to 15 4 ng/mL. The metabolite flurbiprofen inhibited plasma COX-1 activity for the duration of the study period (maximum inhibition at 4 hours), whereas COX-2 activity recovered after 6 hours. In the crossover study, levels of gastric NO were higher in subjects given nitroflurbiprofen, when compared with those given flurbiprofen. (The area under the curve for gastric NO was 435 +/- 107 ppm (.) h versus 305 +/- 94 ppm (.) h [95% confidence interval of the difference, 89-172 ppm (.) h; P <.001]). Conclusion: Nitroflurbiprofen was undetectable in the systemic circulation, suggesting metabolism to (15)N-nitrate/nitrite and flurbiprofen in the presystemic circulation. Levels of gastric NO were significantly higher after ingestion of nitroflurbiprofen than flurbiprofen.