Peripheral analgesic sites of action of anti-inflammatory drugs

Inflammatory signs and symptoms of redness, swelling, heat and pain are due to the effects of inflammatory mediators released during the inflammatory response. Depending on the type of injurious stimuli and the tissue involved, the array of mediators may differ but eicosanoids are involved in the genesis of inflammatory pain. They are responsible for the hypersensitisation of the nociceptors (allodynialhyperalgesia). The basic mechanism of analgesic action of nonsteroidal anti-inflammatory drugs results from the inhibition of prostaglandin synthesis (prostacyclin or PGE2), thus preventing nociceptor threshold lowering. Because there is a temporal hierarchy in the release of inflammatory mediators, there are several targets for the action of peripheral acting analgesics before and after the inhibition of prostaglandin synthesis. Blockade of the release and inhibition of inducible cyclooxygenase explain the analgesic action of glucocorticoids. Nimesulide also has an inhibitory action on the cascade of hypersensitising cytokines. Some analgesics, such as dipyrone, flurbiprofen or diclofenac, act directly upon ongoing inflammatory hypersensitisation. Those analgesics restore the nociceptor by stimulating the arginine/NO/cGMP/K(ATP) channel pathway.     

Effect of gender on anti-inflammatory and analgesic actions of two kappa-opioids

The higher incidence of inflammatory and painful disorders in women and recent reports that have emphasized the importance of gender in nociceptive sensitivity and responsiveness to analgesics prompted us to investigate gender as a factor in the variability in response to opioids. We studied the anti-inflammatory and antinociceptive effects of two kappa-opioid agonists in adjuvant-induced arthritis, one that acts both peripherally and centrally (PNU50488H; 20 mg/kg/day), the other which is peripherally selective (asimadoline; 5 mg/kg/day). Both drugs had equally powerful anti-inflammatory effects in both male and female rats (reducing measures by 60-80%). In contrast, there were gender-based heterogeneities in their analgesic actions, contingent on the method of stimulation (mechanical or thermal); males were insensitive to the analgesic effects of asimadoline with thermal but not mechanical nociceptive stimuli. We also sought evidence for gender influences on the joint content of Substance P (SP), a peptide suggested to have a role in producing inflammation and found that levels were higher in the untreated arthritic females, although there were no gender differences in disease sensitivity or nociception in arthritic animals receiving no drugs. Paradoxically, both drugs elevated SP concentrations in the joints, perhaps as a consequence of an action of kappa-opioids to suppress SP release from peripheral nerves, but the gender differences remained. Further experiments are required to determine exact mechanisms responsible for the gender distinction in analgesic response to kappa-opioids that may involve differential activation of primary afferents.     

Low-dose tizanidine with nonsteroidal anti-inflammatory drugs for detoxification from analgesic rebound headache

OBJECTIVE: To describe an outpatient regimen for analgesic detoxification and resolution of analgesic rebound headache. BACKGROUND: Frequent analgesic use is believed to promote the transformation of episodic migraine into a chronic, pervasive headache syndrome. Management of pain precipitated by analgesic withdrawal is crucial to treatment success. Outpatient treatment protocols designed to achieve successful withdrawal will reduce costs and potentially lead to more widespread implementation of therapy. METHODS: Patients with appropriate histories were managed on an outpatient basis for detoxification by discontinuation of the offending analgesic and initiation of treatment with tizanidine and a long-acting nonsteroidal anti-inflammatory drug. Patients kept diaries of pain and medication use. Results were evaluated at 6 and 12 weeks. Patients able to tolerate no or trivial analgesic use (ie, 4 or fewer doses in each 2-week period) were considered responders. RESULTS: At 6 weeks, 36 patients (65%) were responders. At 12 weeks, 38 patients (69%) were responders. The chronic daily headache pattern had resolved at 12 weeks in 34 patients (62%). CONCLUSIONS: This treatment protocol was well tolerated and yielded a high degree of efficacy, demonstrating that outpatient management can be effective for achieving analgesic withdrawal and resolution of analgesic rebound headache.     

Nonsteroidal anti-inflammatory drugs efficiently reduce the transport and cytotoxicity of adefovir mediated by the human renal organic anion transporter 1

Adefovir is a nucleotide analog with anti-human immunodeficiency virus (HIV) activity that has been extensively studied in clinical trials. While on prolonged anti-HIV therapy with adefovir, some patients may develop drug-associated nephrotoxicity manifested by changes in laboratory markers of renal tubular functions that are reversible upon drug discontinuation. It has been recently shown that adefovir is efficiently transported by the human renal organic anion transporter 1 (hOAT1), a membrane transport protein localized in the kidney, that presumably mediates the accumulation of adefovir in renal proximal tubules. In an effort to look for novel inhibitors of this transport process, we used a cell line stably expressing hOAT1 to demonstrate that nonsteroidal anti-inflammatory drugs (NSAIDs) efficiently inhibit hOAT1-specific transport of adefovir at clinically relevant concentrations. Diflunisal, ketoprofen, flurbiprofen, indomethacin, naproxen, and ibuprofen were equally or more effective (IC(50) = 0.85-8 microM) than probenecid or betamipron, two known potent inhibitors of hOAT1 (IC(50) = 8 and 6 microM, respectively) with in vivo nephroprotective effects. Importantly, NSAIDs significantly reduced the shift in adefovir cytotoxicity observed upon hOAT1 expression with ketoprofen and naproxen being 2- to 3-times more effective than probenecid. Transport experiments with [(3)H]ketoprofen and [(3)H]ibuprofen revealed that NSAIDs themselves were not efficiently transported by hOAT1. None of the NSAIDs tested showed any interference with the anti-HIV activity of adefovir. In conclusion, these observations suggest that NSAIDs may reduce or delay the emergence of adefovir nephrotoxicity.     

Interactions of human organic anion transporters and human organic cation transporters with nonsteroidal anti-inflammatory drugs

The purpose of this study was to elucidate the interactions of human organic anion transporters (hOATs) and human organic cation transporters (hOCTs) with nonsteroidal anti-inflammatory drugs (NSAIDs) using cells stably expressing hOATs and hOCTs. NSAIDs tested were acetaminophen, acetylsalicylate, salicylate, diclofenac, ibuprofen, indomethacin, ketoprofen, mefenamic acid, naproxen, piroxicam, phenacetin, and sulindac. These NSAIDs inhibited organic anion uptake mediated by hOAT1, hOAT2, hOAT3, and hOAT4. By comparing the IC(50) values of NSAIDs for hOATs, it was found that hOAT1 and hOAT3 exhibited higher affinity interactions with NSAIDs than did hOAT2 and hOAT4. HOAT1, hOAT2, hOAT3, and hOAT4 mediated the uptake of either ibuprofen, indomethacin, ketoprofen, or salicylate, but not acetylsalicylate. Although organic cation uptake mediated by hOCT1 and hOCT2 was also inhibited by some NSAIDs, hOCT1 and hOCT2 did not mediate the uptake of NSAIDs. In conclusion, hOATs and hOCTs interacted with various NSAIDs, whereas hOATs but not hOCTs mediated the transport of some of these NSAIDs. Considering the localization of hOATs, it was suggested that the interactions of hOATs with NSAIDs are associated with the pharmacokinetics and the induction of adverse reactions of NSAIDs.     

Dynamic regulation of gastric surface pH by luminal pH

In vivo confocal imaging of the mucosal surface of rat stomach was used to measure pH noninvasively under the mucus gel layer while simultaneously imaging mucus gel thickness and tissue architecture. When tissue was superfused at pH 3, the 25 microm adjacent to the epithelial surface was relatively alkaline (pH 4.1 +/- 0.1), and surface alkalinity was enhanced by topical dimethyl prostaglandin E2 (pH 4.8 +/- 0.2). Luminal pH was changed from pH 3 to pH 5 to mimic the fasted-to-fed transition in intragastric pH in rats. Under pH 5 superfusion, surface pH was relatively acidic (pH 4.2 +/- 0.2). This surface acidity was enhanced by pentagastrin (pH 3.5 +/- 0.2) and eliminated by omeprazole, implicating parietal cell H,K-ATPase as the dominant regulator of surface pH under pH 5 superfusion. With either pH 5 or pH 3 superfusion (a) gastric pit lumens had the most divergent pH from luminal superfusates; (b) qualitatively similar results were observed with and without superfusion flow; (c) local mucus gel thickness was a poor predictor of surface pH values; and (d) no channels carrying primary gastric gland fluid through the mucus were observed. The model of gastric defense that includes an alkaline mucus gel and viscous fingering of secreted acid through the mucus may be appropriate at the intragastric pH of the fasted, but not fed, animal.     

Developmental adaptations in cytosolic phosphate content and pH regulation in the sheep heart in vivo.

This study examines adaptations in myocardial cytosolic phosphate content and buffering capacity that occur in vivo as a function of development. Phosphate metabolites were monitored in an open chest sheep preparation using a 31P magnetic resonance surface coil over the left ventricle. Newborn lambs (aged 4-9 d, n = 5) underwent exchange transfusion with adult blood to reduce blood-borne 2,3-diphosphoglycerate contamination of the heart monophosphate and phosphomonoester resonances, thus allowing determination of these phosphate concentrations. The blood-exchanged newborns and mature controls (aged 30-60 d, n = 5) were infused with 0.4 N hydrochloric acid to decrease pH from greater than 7.35 to less than 7.00. Simultaneously, intracellular and extracellular pH were determined from the chemical shifts of the respective phosphate peaks and compared to arterial blood pH. Findings were as follows: (a) diphosphoglycerate contribution to the cardiac spectrum was found to be negligible, (b) significant decreases in cytosolic phosphate (P less than 0.03) and phosphomonoester (P less than 0.01) content occurred with maturation, and (c) large decreases in extracellular pH (greater than 0.5 U) in both groups were similarly associated with only small changes in intracellular pH (less than 0.1 U). Change in cytosolic phosphate content implies that alterations occur in the phosphorylation potential with resulting effects on regulation of myocardial respiration, and cardiac energetics.     

Practical points on nonsteroidal anti-inflammatory drugs

All nonsteroidal anti-inflammatory drugs act by inhibiting prostaglandin synthesis, but the particular agent that will best suit an individual patient's needs cannot be predicted. Each drug should be tried for at least three weeks at maximal dosage before it is considered ineffective. When a particular nonsteroidal anti-inflammatory agent is not effective, one from another class should be tried. Levels of drugs metabolized by the liver are altered by nonsteroidal anti-inflammatory agents. Costs are quite variable.     

非甾体抗炎药对锁骨骨折患者术后愈合的影响

目的探讨非甾体抗炎药对锁骨骨折患者术后愈合的影响,为临床用药提供依据。方法将120例锁骨骨折术后患者随机分为试验组和对照组,每组60例,试验组于术后第1天开始口服塞来昔布200 mg,2次/d,疗程7 d,对照组不给予任何非甾体抗炎药及阿片类镇痛药;采用VAS评分评估两组患者术后疼痛情况,记录不良事件;于术后4、8、12周对两组患者骨折部位进行X线检查,评估骨折愈合情况。结果采用塞来昔布治疗后,试验组患者VAS评分较对照组降低（4.08±1.05分 vs 8.07±0.84分, P<0.05）,4、8、12周的骨膜反应评分均高于对照组（1.15±0.33、2.02±0.34、2.60±0.49分,P<0.05）,而骨痂出现率、骨折愈合评分、骨骼塑形评分均低于对照组（P<0.05）。结论非甾体抗炎药塞来昔布对锁骨骨折的愈合可能具有不利影响。