© 2008 The Authors Doi: 10.1111/j.1742-7843.2008.00332.x Journal compilation © 2008 Nordic Pharmacological Society . Basic & Clinical Pharmacology & Toxicology , 104, 17–21 Blackwell Publishing Ltd Effects of Nimesulide, Acetylsalicylic Acid, Ibuprofen and Nabumetone on Cyclooxygenase-1- and Cyclooxygenase-2-Mediated Prostanoid Production in Healthy Volunteers ex vivo Markku Kerola 1 , Katriina Vuolteenaho 1 , Outi Kosonen 1 , Hannu Kankaanranta 1 , Seppo Sarna 2 and Eeva Moilanen 1 1 The Immunopharmacology Research Group, Medical School, University of Tampere, and Research Unit, Tampere University Hospital, Tampere, Finland, and 2 Department of Public Health, University of Helsinki, Helsinki, Finland (Received November 28, 2007; Accepted August 20, 2008) Abstract: The beneficial actions of non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with inhibition of cyclooxygenase-2 (COX-2), whereas some of their adverse effects are associated mainly with inhibition of COX-1. Selec- tive COX-2 inhibitors reduce the risk of gastrointestinal adverse events, but increase the risk of thromboembolic events pointing to importance of optimal COX-1/COX-2 inhibition in drug safety. We compared the effects of acetylsalicylic acid, ibuprofen, nabumetone and nimesulide on COX-1 and COX-2 pathways in healthy volunteers in an ex vivo set-up using single oral doses commonly used to treat acute pain. In a randomized, double-blind four-phase cross-over study, 15 healthy volunteers were given orally a single dose of either acetylsalicylic acid 500 mg, ibuprofen 400 mg, nabumetone 1 g or nimesulide 100 mg. Blood samples were drawn before and 1, 3, 6, 24 and 48 hr after the drug for the assessment of COX-1 and COX-2 activity. COX-1 activity was measured as thromboxane 2 production during blood clotting and COX-2 activity as endotoxin-induced prostaglandin E 2 synthesis in blood leucocytes. The data show that after a single oral dose these four NSAIDs have different profiles of action on COX-1 and COX-2. As expected, acetylsalicylic acid appeared to be COX-1- selective and ibuprofen effectively inhibited both COX-1 and COX-2. Nabumetone showed only a slight inhibitory effect on COX-1 and COX-2. Nimesulide caused almost complete suppression of COX-2 activity and a partial reduction of COX-1 activity. This confirms the relative COX-2 selectivity of nimesulide. The discovery of a second form of cyclooxygenase (COX) nearly 20 years ago has changed our understanding on the mechanisms of the therapeutic and adverse effects of non- steroidal anti-inflammatory drugs (NSAIDs). A hypothesis was introduced by Sir John Vane in 1994 [1] that the antipyretic, analgesic and anti-inflammatory actions of NSAIDs result from inhibition of the inducible COX-2, whereas many of the common adverse effects, especially NSAID gastropathy, are due to inhibition of the constitutive COX-1. Selective COX-2 inhibitors reduce the risk of gastrointestinal adverse events [2–5], but recent large-scale studies have pointed to increased risk of thromboembolic events [6 –9]. Based on this, semi-selective COX-2 inhibitors may have favourable risk profile with reduced risk of gastrointestinal adverse events and without increased risk of thromboembolic events. Non-steroidal anti-inflammatory drugs are classified into selective COX-1 inhibitors, non-selective COX inhibitors, semi- selective COX-2 inhibitors and selective COX-2 inhibitors according to their relative potency against the two forms of COX based on the data from in vitro and animal studies [10–13]. Due to several confusing factors associated with the in vitro models, these results are not directly applicable for COX-1/COX-2 selectivity in man, and there is only limited information comparing the COX-1/COX-2 selectivity of various NSAIDs after therapeutic doses in man. The present study was designed to investigate the COX-1/COX-2 selec- tivity of two widely used NSAIDs (acetylsalicylic acid and ibuprofen) in an ex vivo set-up and two semi-selective COX-2 inhibitors (nabumetone and nimesulide) based on in vitro data and favourable gastric safety profile. Materials and Methods Fifteen healthy volunteers (age range, 21–30 years, eight men) were recruited from medical students. Persons with a history of gastritis or gastroduodenal ulcerations were not included in the study. Apart from oral contraceptives, none of the volunteers had any medication. They were all non-smokers and had body mass index <30. All volunteers provided written consent to participate in the study, and the study was approved by the Ethics Committee of the Tampere University Hospital. Study design. A randomized, double-blind, cross-over study design in four phases was used. The phases were separated by an interval of 3 weeks. The volunteers were given orally a single dose of either acetylsalicylic acid 500 mg (Aspirin, Bayer, Germany), ibuprofen 400 mg (Burana, Orion Pharma, Finland), nabumetone 1 g (Relifex, SmithKline, Beecham, UK) or nimesulide 100 mg (Nimed, Aventis Pharma, Finland). The volunteers fasted for 8 hr before administra- tion of a drug and continued fasting for another 2 hr. Blood samples were drawn immediately before administration of a drug (0 hr) and after 1, 3, 6, 24 and 48 hr for the assessment of whole blood prostaglandin 2 and platelet thromboxane 2 production. Author for correspondence: Eeva Moilanen, The Immunopharma- cology Research Group, Medical School, 33014 University of Tampere, Finland (fax +358 3 3551 8082, e-mail eeva.moilanen@uta.fi).