The Experimental Study On The Pharmacological Action Of Morphine Combined With Lornoxicam On The Acute Pain

BackgroundThe combination of drugs has been widely uesed in clinical and basal reasearch,especially in drug therapy of pain,which was a common practice for enhancing the efficiency and reducing the adverse effects of drug treatment.Morphine,as an opioid agonist,has significantly analgesic effect,but its adverse effect such as respiratory depression,sedative,nausea,vomiting limited its administration in clinical practice.Lornoxicam is a new and injectable non-steroidal anti-inflammatory drug(NSAID),and was extensively applied to treat acute and chornic pain as its low side effects.The analgesic mechansim of lornoxicam was produced not only by way of inhabiting cyclooxygenase(COX) to restrain the synthesis of the peripheral prostaglandids(PGs),but also by way of activating the endogenous opioid peptides system.So the combination of morphine and lornoxicam was uesd to preemptive analgesia and postoperative analgesia and provided more effective analgesia than the others.However,the synergism between opioid agonists and NSAIDs was not still understood completely and selection of the optimal combination and the optimal doses remainsa matter of trial and error.The present study was undertaken to evaluate the antinociceptive interaction between morphine and lornoxicam and searched the best compatibility which was more effective and less adverse.Part one Pharmacodynamic study on the combination of morphine and lornoxicam in ratsExperiment 1 Analgesic effect of morphine combined with lornoxicam in different propotions in ratsObjective To compare the analgesic effect of morphine combined with lornoxicam in different propotions in rats.Methods 56 male adult SD rats were divided randomly into eight groups:Groupâ… received hypodermic injection of 1ml 0.9%NaCl,GroupⅡ～Ⅷreceived hypodermic injection of morphine combined with lornoxicam in different propotions(6mg·kg^-1/0mg·kg^-1, 1mg·kg^-1/5mg·kg^-1·2mg·kg^-1/4mg·kg^-1·3mg·kg^-1/3mg·kg^-1, 4mg·kg^-1/2mg·kg^-1·5mg·kg^-1/1mg·kg^-1and 0mg·kg^-1/6mg·kg^-1)respectively. Pain behavior was assessed by withdrawal threshold to CO₂ laser stimulation at 15,30,60,120min after administration.Else 54 male adult SD rats were assigned randomly into nine groups.Under the 1.4%isoflurane anesthesia,an incision of 1cm long was made in the plantar region of left hindpaw parallel to the muscle according to the method of Brennan.Group A inhaled 1.4% isoflurane for 5 min but no incision was made,Group B received hypodermic injection of 1ml 0.9%NaCl after incision,Group C～H and Group L recived hypodermic injection of morphine combined with lornoxicam in different doses, which were same to GroupⅡ～Ⅷrespectively.Cumulative pain score were observed within 1 hour afer administration.Results In the first experiment,the pain thresholds of rats in GroupⅡ～Ⅷbegan to increase at 15min after administration,the peak values were obtained at 30min.And the effect could remain till 120min after administration(Comepared with Groupâ… ,P<0.01 or P <0.05).The pain threshold of rats in Groupâ…£,â…¤,â…¥were significantly higher than those in other groups at 30min,and the values of Groupâ…¤andâ…¥,meaured at 60min,were also higher than the other.In the second experiment,the cumulative pain scores of rats in Group B was significantly higher than the other groups.The scores in Group C,F,G and H all showed statstic differences, compared with Group D and Group E.Conclusion Morphine combined with lornoxicam in propotion of 1:1～1:0.5 provides more powerful analgesic effect because of their potential synergistic effect. Experiment 2 Adverse effects of morphine combined with lornoxicam in different propotions in ratsObjective To compare the adverse effects of morphine combined with lornoxicam in different propotions in rats.Methods 48 male SD rats(200～250g)were divided randomly into eight groups:Group A received hypodermic injection of 1ml 0.9%NaCl,Group B～H received hypodermic injection of morphine combined with lornoxicam in different propotions (6mg·kg^-1/0mg·kg^-1,1mg·kg^-1/5mg·kg^-1,2mg·kg^-1/4mg·kg^-1, 3mg·kg^-1/3mg·kg^-1,4mg·kg^-1/2mg·kg^-1,5mg·kg^-1/1mg·kg^-1and 0mg·kg^-1/6mg·kg^-1)respectively.Respiratory frequency were measured before administration and at 15,30,60,120min after administration.In addition, Open-field test was executed to measure the behaviors of the rats at 30min after administration.Else 48 male SD rats were assigned randomly into eight groups similar to the above grouping.All rats were breeded in metabolic cage,when the characteristic of kaolin intake,egestion and urination of the rats were observed respectively within 24hrs after administration.Results In the first experiment,the respiratory frequency of rats in each group showed different changing after administration,which did not reveal the relationship with the proportions or doses of drugs obviously.In open-field test,the scores of B,D～G group were significantly lower than A,C and H group which did not show statistic difference among them.In the second experiment,the weight of Kaolin intake of rats in Group B was significantly higher than Group A.The weight of Kaolin intake in Group C,D,E and H all showed statistic differences,compared with Group B,F and Group G.Moreover,the weight of feces and Urine volume in Group A were higher than Group B,F and G,while they did not show statistic difference compared with Group C,D,E and H.Conclusion Morphine combined with lornoxicam will induce less adverse effects when their compatibility is in the proportion of 1:1 or lower in rats. Experiment 3 The study on dose-effect relationship and interaction of morphine combined with lornoxicam in ratsObjective To study the dose-effect relationship of morphine combined with lornoxicam in the proportion of 1:1 and the interaction type of morphine with lornoxicam such as synergistic,additive and antagonistic.Methods 35 male SD rats weighting 200～250g were radomly divided into five groups:Group A received hypodermic injection of 1ml 0.9%NaCl,GroupB received hypodermic injection of morphine 4mg/kg,Group C～E received hypodermic injection of morphine with lornoxicam(4mg·kg^-1/4mg·kg^-1,2mg·kg^-1/2mg·kg^-1, 1mg·kg^-1/1mg·kg^-1)respectively.Pain behavior was assessed by withdrawal threshold to CO₂ laser stimulation at 15,30,60,120min after administration and the percentage of changes in pain theshold.Else 24 male SD rats weighting 200～250g were radomly divided into three groups:Group M was administered morphine 4mg/kg by hypodermic injection,Group L was administered lornoxicam 4mg/kg by hypodermic injection,and Group M+L was administered morphine 4mg/kg and lornoxicam 4mg/kg by hypodermic injection.All rats received CO₂ laser stimulation at 15,30,60,120min after administration and measurment of claw withdrawal threshold.The interaction type was estimated by Q value provided by Jin Zhengjun's method.Results In the experiment of does-effect relationship,the pain thresholds of rats in Group B～E began to increase at about 15min aider administration,the peak values were obtained at 30min.And the effect could remain till 120min after administration in Group B, C,and D.The pain thresholds of rats in Group C,D,and E showed statistic difference,and increased along with the drug dose increasing at parallel time. And in the evaluation of interaction of morphine and lornoxicam,the analgesic effect of the combination was significantly higher than morphine or lornoxiam alone administerd.The Q value at 60min after administration was calculated, and the result of Q=1.18>1.15 indicated that the two drugs provided significant synergism.Conclusion The analgesia provided by morphine combined with lornoxicam in propotion of 1:1 is dose-dependent in the dosage range in this study.The combination of morphine and lornoxicam have a synergistic effect.Part two Pharmacokinetics study on the combination of morphine and lornoxicam in ratsObjective To study the Pharmacokinetics of the combination of morphine and lornoxicam in rats,and approach the interaction of morphine and lornoxicam. Methods 24 male adult SD rats were randomly divided into three groups:Group M(n=6)received received hypodermic injection of morphine 2mg/kg,Group L (n=6)received hypodermic injection of lornoxicam 2mg/kg,and Group M+L (n=12)received hypodermic injection of morphine 2mg/kg and lornoxicam 2mg/kg.All rats were fasting for 12hrs before administration,then lornoxxicam concentrations in plasma,which were obtained respectively from the eye sockets at 1h before administration and at 0.17,0.25,0.5,1,2,4,6,8 and 12h after administration,were determined by high performance liquid chromatography (HPLC).The morphine concentrations in plasma,which were obtained at 1h before administration and at 0.17,0.25,0.5,0.45,1,1.5 and 2h after administration,were determined by HPLC.The software DAS 2.1.1 was emploied in the pharmacokinetic parameters analyses.Results The compare of pharmacokinetics parameters,such as T_max,C_max,V/F,AUC,T_1/2and CL/F, between morphine or lornoxicam administered alone and combination of the two drugs showed no statistic differences.Conclusion Morphine and lornoxicam had no influences with each other on pharmacokinetics when their combination was administered in rats.