title: Enhancement of antinociception by co-administration of an opioid drug (morphine) and a preferential cyclooxygenase-2 inhibitor (rofecoxib) in rats.
abstract: Synergism has been used to obtain analgesia at doses at which side effects are minimal. In addition, it has been demonstrated that inhibition of cyclooxygenase-2 is responsible for the therapeutic effects of nonsteroidal anti-inflammatory drugs (NSAIDs). The aim of this study was to evaluate the antinociceptive interaction between the preferential COX-2 inhibitor, rofecoxib and morphine. Several combinations were evaluated using the pain-induced functional impairment model (PIFIR), a rat model of arthritic pain. Surface of synergistic interaction (SSI) analysis and an isobolographic method were used to detect the antinociceptive potency of the drugs, given either individually or in combination. The surface of synergistic interaction was calculated from the total antinociceptive effect produced by the combination after subtraction of the antinociceptive effect produced by each individual drug. Male rats received orally morphine alone (10, 17.8, 31.6, 56.2 and 100.0 mg/kg), rofecoxib alone (3.2, 5.6, 10, 31.6, 56.2 and 74.0 mg/kg) or 12 different combinations of morphine and rofecoxib. Three combinations exhibited potentiation of antinociceptive effects (10 mg/kg of morphine with either 5.6, 10 or 31.6 mg/kg of rofecoxib), whereas the other nine combinations showed additive antinociceptive effects. The combination of morphine, 56.2 mg/kg (p.o.), and rofecoxib, 31.6 mg/kg (p.o.), produced the maximum antinociceptive effect (P<0.05). This combination caused gastric injuries less severe than those observed with indomethacin, i.e. it reduced ulcers and erosion formation. The synergistic antinociceptive effects of rofecoxib and morphine are important and suggest that combinations with drugs may decrease the side effects associated with the use of nonselective NSAIDs. Furthermore, the present results suggest that combinations containing opioid drugs and selective COX-2 inhibitors may have clinical utility in pain therapy.
authors.affiliation: Departamento de Farmacobiología, Lab. No. 7 Dolor y Analgesia, CINVESTAV-IPN, Calz. de los Tenorios No. 235, Col. Granjas Coapa, Deleg. Tlálpan, C.P. 14330 México D.F., México.
authors.forename: Myrna
authors.initials: M
authors.lastname: Déciga-Campos
authors.forename: Uriah Guevara
authors.initials: UG
authors.lastname: López
authors.forename: Maria Irene Díaz
authors.initials: MI
authors.lastname: Reval
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: López-Muñoz
mesh_terms: D000284:Administration, Oral; D000700:Analgesics / Q000009:adverse effects / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000009:adverse effects / Q000494:pharmacology*; D000818:Animals; D018771:Arthralgia / Q000139:chemically induced / Q000517:prevention & control; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D007527:Isoenzymes / Q000187:drug effects* / Q000378:metabolism; D007783:Lactones / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D009020:Morphine / Q000009:adverse effects / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach / Q000187:drug effects / Q000473:pathology; D013276:Stomach Ulcer / Q000139:chemically induced; D013450:Sulfones; D013997:Time Factors; D014527:Uric Acid / Q000008:administration & dosage
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D007783:Lactones; D013450:Sulfones; C116926:rofecoxib; D014527:Uric Acid; D009020:Morphine; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases