Non-steroid anti-inflammatory drugs: influence of extra-cellular pH on biodistribution and pharmacological effects

Pharmacogenomics of NSAID-Induced Upper Gastrointestinal Toxicity

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of drugs which are widely used globally for the treatment of pain and inflammation, and in the case of aspirin, for secondary prevention of cardiovascular disease. Chronic non-steroidal anti-inflammatory drug use is associated with potentially serious upper gastrointestinal adverse drug reactions (ADRs) including peptic ulcer disease and gastrointestinal bleeding. A few clinical and genetic predisposing factors have been identified; however, genetic data are contradictory. Further research is needed to identify clinically relevant genetic and non-genetic markers predisposing to NSAID-induced peptic ulceration.

Aspirin as a potential treatment in sepsis or acute respiratory distress syndrome

Sepsis is a common condition that is associated with significant morbidity, mortality and health-care cost. Pulmonary and non-pulmonary sepsis are common causes of the acute respiratory distress syndrome (ARDS). The mortality from ARDS remains high despite protective lung ventilation, and currently there are no specific pharmacotherapies to treat sepsis or ARDS. Sepsis and ARDS are characterised by activation of the inflammatory cascade. Although there is much focus on the study of the dysregulated inflammation and its suppression, the associated activation of the haemostatic system has been largely ignored until recently. There has been extensive interest in the role that platelet activation can have in the inflammatory response through induction, aggregation and activation of leucocytes and other platelets. Aspirin can modulate multiple pathogenic mechanisms implicated in the development of multiple organ dysfunction in sepsis and ARDS. This review will discuss the role of the platelet, the mechanisms of action of aspirin in sepsis and ARDS, and aspirin as a potential therapy in treating sepsis and ARDS.

pH-responsive biodegradable assemblies containing tunable phenyl-substituted vinyl ethers for use as efficient gene delivery vehicles

Novel pH-responsive assemblies (PEG-lipid:DOPE liposomes) containing tunable and bifunctional phenyl-substituted vinyl ether (PIVE) cross-linkers were prepared. The assemblies consisted of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), acid-cleavable poly(ethylene glycol) (PEG)-conjugated lipids, pDNA, and protamine sulfate (PS). The PIVE linkage was designed to hydrolyze under acidic conditions, and the hydrolysis studies of PEG-lipid compounds containing PIVE at pH 4.2, 5.4, and 7.4 indicated that the hydrolysis rates of PIVE linker were influenced by the substitution of electron withdrawing or electron donating groups on the phenyl ring. Acid-catalyzed hydrolysis of PIVE leads to destabilization of the acid labile PEG-PIVE-lipid:DOPE liposomes via dePEGylation, thereby triggering content release. Content release assays showed that dePEGylation was highly pH-dependent and correlated with the PIVE proton affinity of the phenyl group. These results indicated that the dePEGylative triggering based on a new pH-sensitive PIVE linkage can be controlled. In vitro transfection studies on the pH-responsive assemblies containing mPEG-(MeO-PIVE)-conjugated 1,3-dioctadecyl-rac-glycerol lipids (mPEG-(MeO-PIVE])-DOG) showed higher transfection efficiency compared to that of polyethylenimine (PEI), a positive control, on HEK 293 and COS-7 cells. In addition, lower cytotoxicity of PEG-PIVE-lipid:DOPE liposomes/PS/DNA was observed in comparison to PEI. These results suggest that PEG-PIVE-lipid:DOPE liposomes can be considered as nonviral vehicles for drug and gene delivery applications.

Acid-triggered release via dePEGylation of fusogenic liposomes mediated by heterobifunctional phenyl-substituted vinyl ethers with tunable pH-sensitivity

A new family of heterobifunctional phenyl-substituted vinyl ether (PIVE) coupling agents with tunable acid-sensitivity has been developed. The PIVE compounds are designed to hydrolyze under acidic conditions with hydrolysis rates that can be varied by rational selection of the phenyl ring substituent. These reagents were incorporated within 2-methoxypoly(ethylene glycol) PEG-conjugated 1,3-dioctadecyl-rac-glycerol lipids to produce the acid-cleavable lipopolymers mPEG-[H-PIVE]-DOG, mPEG-[F-PIVE]-DOG, mPEG-[Me-PIVE]-DOG, and mPEG-[MeO-PIVE]-DOG. These lipopolymers were hydrolyzed under acidic conditions (pH 3.5 or 4.5) at rates that were dependent on the electron donating or withdrawing character of the α-phenyl vinyl ether substituent, while remaining stable at pH 7.4. Blending of these compounds with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in a 10:90 mPEG-PIVE-Lipid:DOPE ratio produced stable liposomes at neutral pH; however, acidification of the solution led to dePEGylation and release of the liposomal cargo in a manner that correlated with the PIVE proton affinity. Specifically, we observed 70% calcein release within 12 h from mPEG-[MeO-PIVE]-DOG-containing liposomes at pH 4.5, whereas only 22% calcein release was observed from mPEG-[F-PIVE]-DOG:DOPE liposomes over this same time scale and pH. These results indicate that dePEGylation following acidification is a triggering mechanism that can be rationally designed and controlled through the appropriate selection of PIVE moieties.

Tuning the pH sensitivities of orthoester based compounds for drug delivery applications by simple chemical modification

Orthoesters are acid-sensitive moieties that allow substantial structural diversity for biological applications including drug delivery. Here, the pH-sensitivity of a range of novel orthoester based compounds was compared in the range 7.5-4.5 that is characteristic of the increased acidification during endocytosis. We find that simple modifications close to the orthoester had major effects on both the rate and extent of hydrolysis, suggesting this could be exploited for activating drug delivery systems on endocytic pathways.

Cyclooxygenase-2 inhibitors: promise or peril?

The discovery of two isoforms of the cyclooxygenase enzyme, COX-1 and COX-2, and the development of COX-2-specific inhibitors as anti-inflammatories and analgesics have offered great promise that the therapeutic benefits of NSAIDs could be optimized through inhibition of COX-2, while minimizing their adverse side effect profile associated with inhibition of COX-1. While COX-2 specific inhibitors have proven to be efficacious in a variety of inflammatory conditions, exposure of large numbers of patients to these drugs in postmarketing studies have uncovered potential safety concerns that raise questions about the benefit/risk ratio of COX-2-specific NSAIDs compared to conventional NSAIDs. This article reviews the efficacy and safety profiles of COX-2-specific inhibitors, comparing them with conventional NSDAIDs.

Uptake of ibuprofen, indomethacin and ketoprofen into isolated rabbit parietal cells

In the United States and other countries, non-steroidal anti-inflammatory drugs (NSAIDs) can be purchased without a prescription. Due to their widespread use, the drugs' most common side effect, gastric toxicity, becomes a more serious concern. Gastric toxicity can occur directly by contact with mucous membranes or indirectly by the inhibition of prostaglandin production in the gastric mucosa. We have studied the uptake of NSAIDs in gastric tissue, specifically parietal cells removed from the rabbit stomach. New Zealand White rabbits were killed and then used to harvest parietal cells. The purified cells were used to study the uptake of ibuprofen, indomethacin and ketoprofen (NSAIDs) over time and under different experimental conditions. The effects of concentration were investigated for all three NSAIDs. In addition, indomethacin and ibuprofen were used to investigate the mechanism of uptake. Studies were determined for the effects of varied extracellular pH from pH 6 to 8, and inhibitory conditions from depressed temperature (5 degrees C), metabolic inhibitors (sodium azide and 2,4-dinitro-phenol), an ionophore (nigericin) and a sodium free support medium. The interaction of NSAIDs with lysed parietal cells was investigated also. Initial rate data indicated that Michaelis-Menten kinetics were apparent; however, poor solubility of all three NSAIDs prevented complete characterization of the inclusion of a passive transport mechanism. Uptake showed a statistically significant increase (P = 0.01 to 0.05) as pH decreased, also suggesting contribution from a passive mechanism. Studies with inhibitors showed minimal effects. However, uptake at equilibrium for the ionophore, nigericin, showed a 10-fold increase over the control for ibuprofen (P = 0.005) and a 1.4-fold increase for indomethacin (P=0.04). Depressed temperature (5 degrees C) increased the initial rate and uptake at equilibrium 2.1- and 2.2-fold, respectively, for ibuprofen (P < 0.01). For indomethacin depressed temperature increased the initial rate and uptake at equilibrium 2.7- and 5.2-fold, respectively (P < 0.01). The increases at 5 degrees C suggests that adsorption may be an important uptake component. Experiments with lysed parietal cells showed a non-specific uptake phenomenon, suggesting an adsorption component was occurring also.

Nimesulide: an NSAID that preferentially inhibits COX-2, and has various unique pharmacological activities

Nimesulide is a NSAID with good anti-inflammatory, analgesic and antipyretic activities expected of such compounds. However, in addition it has some unique therapeutic and pharmacological activities. The novel therapeutic aspects include a relatively low toxicity to the gastrointestinal tract and kidneys, it can be given to most patients who experience respiratory problems with other NSAIDs, and the onset of analgesia is comparatively quick. The main novel pharmacological actions obtained using nimesulide in vivo at therapeutic doses, or in vitro at concentrations within the therapeutic range of free (unbound) drug, include: a preferential inhibition of prostaglandin synthesis via COX-2, and reductions in cytokine action/release, histamine release, the release of enzymes that degrade cartilage, and the release of superoxide anions and other toxic substances from neutrophils. Interactions with other drugs are few and of little or no clinical significance.

Considerations for nonsteroidal anti-inflammatory drug therapy: safety

Although therapeutically beneficial, nonsteroidal anti-inflammatory drugs are associated with serious gastrointestinal side effects, including ulceration, hemorrhage, and perforation. Endoscopic studies indicate that up to 30% of chronic NSAID users will develop gastroduodenal ulceration. Various case-control studies have reported an association between ulcer-related complications or deaths and NSAID use. An imprecise correlation has been found to exist between the presence of NSAID-induced gastrointestinal damage and symptoms, such as dyspepsia and pain. It is now thought that the major deleterious effects of NSAIDs on the gastrointestinal tract are related to the ability of systemically absorbed NSAIDs to alter gastric and duodenal defense mechanisms, primarily via inhibition of mucosal prostaglandin synthesis. Although various therapeutic agents have been investigated for their ability to prevent NSAID-induced ulcers, only the prostaglandin analogue misoprostol has been shown to significantly reduce the incidence of both gastric and duodenal ulcers in NSAID users. Recently, the Misoprostol Ulcer Complications Outcomes Safety Assessment trial demonstrated that misoprostol also reduces the most serious complications of NSAID-induced ulcers, namely bleeding, perforation, and gastric outlet obstruction.

A new technique for continuous measurement and recording of gastric potential difference in the rat: evaluation of NSAID-induced gastric mucosal damage

Disruption of the gastric mucosal barrier by the so-called "barrier breakers" such as ethanol, aspirin, and bile is associated with an increase in gastric potential difference (GPD), that is, a decrease in its negativity. Because a good correlation between the degree of histological damage and changes in GPD has been observed, this parameter has been used increasingly as an index of mucosal integrity. However, the current methodology for measuring GPD is laborious due to the preparation and checking of KCl-agarose bridges prior to each experiment, and calculations--usually handmade--are time-consuming and inaccurate. In this paper, a new method allowing simultaneous measurement and recording of GPD in the rat is described. The method allows a simultaneous recording of intragastric pH and an automatic data analysis. The new technique has been validated by studying mucosal damage induced by aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) (namely indomethacin and droxicam) as well as the mucosal protective activity of an antacid and sucralfate. The similarity between the results obtained in this rat model and those derived from human experiments clearly show that the developed methodology yields results that are predictive for human pharmacology.

Pharmacokinetics of ketoprofen in healthy horses and horses with acute synovitis

The pharmacokinetic properties of a single intravenous dose of ketoprofen (2.2 mg/kg) in plasma and synovial fluid were compared in four healthy animals and four horses with experimentally induced acute synovitis. Synovitis was induced by the injection of a 1% solution of sterile carrageenan into the left intercarpal joint. Ketoprofen was administered at the same time as carrageenan infection. The plasma disposition followed a biexponential equation or a two-compartment model in most horses. The plasma harmonic mean half-life in healthy horses (0.88 h) was longer than in horses with synovitis (0.55 h). Synovial fluid concentrations of ketoprofen in healthy horses approximated those in plasma by 3 h post-dose. In horses with synovitis, synovial fluid concentrations approximated plasma concentrations by 1 h. Synovial fluid concentrations of ketoprofen in horses with synovitis were 6.5 times higher than those in healthy horses at 1 h. The area under the synovial fluid concentration curve for horses with synovitis was greater than in healthy horses. These data suggest that the inflamed joint serves as a site of sequestration for ketoprofen. Furthermore, these results indicate that plasma pharmacokinetics may be altered by inflammation in a peripheral compartments such as the joint.

Comparative studies of antiplatelet activity of nonsteroidal antiinflammatory drugs and new pyrazine CH- and NH-acids

Nine known nonsteroidal antiinflammatory drugs (NSAID) and three new pyrazine derivatives possessing an active methylene moiety (pyrazine CH/NH-acids) were tested with regards to their in vitro and in vivo antiplatelet activity. Concentrations of the agents were determined which caused 25% and 50% inhibition of aggregation of human blood platelets induced by fixed concentrations of ADP, collagen and epinephrine. The in vivo test consisted in determination of percent protection of mice from pulmonary microembolism caused by injection of a mixture of collagen and epinephrine. The in vitro antiaggregatory activity of the agents studied was rather low, excepting the inhibition of the collagen-induced aggregation by ketoprofen. Several NSAID and two new pyrazine CH/NH-acids appeared highly potent antithrombotic agents in vivo. Activity of NSAID expressed as percent protection against lung thromboembolism in the mouse was demonstrated to depend quantitatively on acid properties of the agents. The new chemical class of pharmacologically active agents, pyrazine CH/NH-acids, offers an original pharmacophore which is distinctive from the carboxylic or enolic functionalities typical for the established NSAID, and as such, may be devoid of some disadvantages of known antiplatelet drugs.

Nonsteroidal anti-inflammatory drugs. Tailoring therapy to achieve results and avoid toxicity

When used appropriately, non-steroidal anti-inflammatory drugs (NSAIDs) are safe and effective for treating pain and inflammation. NSAIDs that block both the lipoxygenase and cyclooxygenase pathways may be advantageous in some patients. New classes of NSAIDs that may have a more favorable safety profile than older agents may improve patient outcome. However, all patients receiving NSAIDs, especially the elderly, should be carefully monitored for possible drug-related complications.

Stereoselective cyclooxygenase inhibition in cellular models by the enantiomers of ketoprofen

The pharmacological activity of rac-ketoprofen and its enantiomers was investigated in vitro using different cellular models. The effect of these compounds on arachidonic acid metabolism was assessed by measuring the inhibition of prostanoid generation under the action of several agonists. Thus, we have evaluated the inhibition of (1) thromboxane B2 synthesis in rabbit platelets and human polymorphonuclear leukocytes (PMNs), (2) prostaglandin E2 synthesis in three cultured cells, namely human umbilical vein endothelial cells (HUVEC), human keratinocytes, and mouse macrophage-like P388D1 cells. The IC50 values found for (+)-(S)-ketoprofen were in the range between 0.1 nM and 0.8 microM, being slightly lower in all models than those found for rac-ketoprofen (0.4 nM-3 microM). On the other hand (-)-(R)-ketoprofen showed inhibition of cyclooxygenase only at concentrations two or three orders of magnitude higher than those required for the (+)-(S) enantiomer. These results, obtained with cell types of relevance for inflammatory processes and with compounds of high optical purity, demonstrate that the prostanoid biosynthesis inhibition caused by the drug rac-ketoprofen is exclusively due to its dextrorotatory enantiomer.

The pharmacokinetics of total and unbound concentrations of tenoxicam in synovial fluid and plasma

Tenoxicam is a nonsteroidal antiinflammatory drug with an elimination half-life of 60-80 hours; it is administered once daily. Tenoxicam concentrations were measured in plasma (10 samples) and synovial fluid (6 samples) over a 24-hour dosage interval at steady state in 10 subjects with arthritis who had been taking the drug at a dosage of 20 mg/day for at least 2 weeks. Total tenoxicam concentrations in synovial fluid were always less than those in plasma, and there was little fluctuation in plasma or synovial concentrations over the dosage interval, although there was substantial inter-subject variation in both concentrations. There was a significant relationship between the tenoxicam dosage when expressed as mg/kg of body weight and the average steady-state total concentration of tenoxicam in plasma (r = 0.80, P = 0.006); this accounted for a substantial proportion of the intersubject variation. The mean +/- SD steady-state concentrations in synovial fluid and plasma were 3.9 +/- 1.8 micrograms/ml and 9.2 +/- 3.7 micrograms/ml, respectively, yielding a mean +/- SD synovial fluid: plasma ratio of 0.43 +/- 0.12. Synovial fluid:plasma ratios of total tenoxicam correlated with synovial fluid:plasma ratios of albumin (r = 0.71, P = 0.02). The synovial fluid:plasma ratio of unbound tenoxicam was 0.90 +/- 0.3 (95% confidence interval 0.68-1.11), which was not significantly different from a value of 1 (t = -1.09, P = 0.31).

The problems and pitfalls of NSAID therapy in the elderly (Part II)

The elderly are most susceptible to pharmacokinetic drug interactions between various NSAIDs and anticoagulants, sulphonylurea hypoglycaemic agents, certain anticonvulsants, methotrexate, digoxin, aminoglycosides and lithium. Pharmacodynamic interactions between some NSAIDs and antihypertensive drugs, anticoagulants, sulphonylurea agents and other NSAIDs are also potentially significant in the elderly. Despite the finding that mean therapeutic responses of large groups of patients have been generally equivalent for the wide range of NSAIDs studied thus far, it is also apparent that marked variability exists in the response of individual patients to different NSAIDs. Subsequent dosage increments may predispose 'nonresponders' and some less sensitive 'responders' to toxicity from NSAIDs. This interindividual variability in response to NSAIDs may be contributed to by the differing physicochemical properties of NSAIDs, physician prescribing habits and patient expectations, variations in NSAID pharmacokinetics, and the differing effects of NSAIDs other than their common ability to inhibit prostaglandin synthesis. The principles for drug prescribing in the elderly are no different from those that should be applied to the prescribing of medication in any patient. The clinician should strive to make a diagnosis and should avoid treating symptoms in isolation. Critical assessment of the indication for prescribing NSAID therapy must include consideration of the available effective and safe alternatives. If an NSAID is commenced the lowest effective dose should be the desired goal, but after an appropriate trial it is acceptable clinical practice to employ an alternative NSAID. There is no justification for combination NSAID therapy. The progress of each patient must be carefully monitored, particularly during the first few months of treatment, while periodic review of the ongoing need for the NSAID is essential.

Dissociation between the antinociceptive and anti-inflammatory effects of the nonsteroidal anti-inflammatory drugs. A survey of their analgesic efficacy

The authors challenge the general view that the analgesic effect of the nonsteroidal anti-inflammatory drugs (NSAIDs) can be universally attributed to their inhibitory effects on the synthesis of peripherally formed prostaglandins. Analgesic activity by some of these compounds in the reduction of physiological pain elicited by a single noxious stimulus, or the treatment of acute pain which results from sudden trauma to otherwise healthy tissue, is better described as an antinociceptive effect. Single-dose studies in the dental pain model that have been conducted in double-blind conditions and included a placebo control group have been reviewed; those NSAIDs which are significantly superior to the reference compound aspirin 650mg and those which could represent real alternatives to the use of narcotics in certain situations for the management of acute pain have been identified. Azapropazone, diflunisal, naproxen, oxaprozin and tolmetin are all weak inhibitors of prostaglandin synthesis, yet they have been shown to be more effective than aspirin. In a model of joint pain, azapropazone 600mg has been shown to be as effective as pethidine (meperidine) 100mg despite being the weakest inhibitor of prostaglandin synthesis. Whether the antinociceptive effect of azapropazone acts at a peripheral or a central level, or both, is not clear; evidence for the effects of NSAIDs on the central nervous system (CNS) is discussed. Historically, the antinociceptive character of some NSAIDs is apparent in several studies in both animals and humans. More recently, experimental algesimetry models designed to distinguish the antinociceptive effects of NSAIDs include the use in humans of photoplethysmography and computer-supported infrared thermographic imaging.

The amphiprotic character of azapropazone and its relevance to the gastric mucosa

Since most non-steroidal anti-inflammatory drugs (NSAIDs) contain only one obvious ionisable group at physiological pH levels then they may be easily identified as having either acidic or basic character. Basic NSAIDs are simply non-acidic NSAIDs capable of accepting a proton within the physiological pH range. Within this range, however, a few NSAIDs contain two obvious ionisable groups, one acidic and the other basic. Such compounds should be described as amphiprotic, and include NSAIDs such as 4- and 5-amino substituted salicylic acids, niflumic acid, amfenac, WY 18251, and azapropazone. The aqueous ionisation equilibrium of such compounds is complex and is described by two macroscopic ionisation constants. Evidence has accumulated during the last decade to support the view that the pharmacokinetic behaviour of NSAIDs contributes not only decisively to their therapeutic effects but also to the type and incidence of their side-effects. A priori, using a physicochemical argument, certain amphiprotic NSAIDs should be better tolerated by the gastric mucosa than the classical acidic compound. Of those NSAIDs commercially available in the United Kingdom azapropazone remains the only one for which amphiprotic behaviour has been described. Following our examination of available data for azapropazone we conclude that the use of amphiprotic compounds represents a logical approach towards solving the problem of NSAID-induced gastric mucosal damage.

Mechanisms of cell association of some non-steroidal anti-inflammatory drugs with isolated leucocytes

In the present study the degree and the mode of association of the radiolabelled drugs acetylsalicylic acid, sodium salicylate, and sodium benzoate with leucocytes were studied in view of the hypothesis that leucocytes are target cells for the anti-inflammatory activity of drugs. The overall association rate of acetylsalicylic acid is larger than that of sodium salicylate and sodium benzoate at 37 degrees, but smaller at 4 degrees. The ratio of the intracellular to the extracellular concentration varied between 1 and 2 for sodium salicylate and sodium benzoate, and between 3 and 6 for acetylsalicylic acid. The intracellular concentrations of these drugs were comparable in red blood cells and polymorphonuclear leucocytes, but lower in mononuclear leucocytes. The association of acetylsalicylic acid and sodium salicylate is markedly increased when the extracellular pH decreases. Lysis of cells decreases the association of acetylsalicylic acid and enhances the association of sodium salicylate and benzoate at 37 degrees twofold. It is suggested that the association of these drugs with leucocytes comprises binding to the membrane and uptake of undissociated species. Phorbol myristate acetate extensively inhibits the intracellular concentration of acetylsalicylic acid, while this inflammatory stimulus tends to increase the intracellular concentration of sodium salicylate. The major metabolites of salicylate enhance cell association of acetylsalicylic acid and salicylic acid. In conclusion, these findings indicate that the tested benzoic acid-like drugs associate with leucocytes in vitro to some extent and that environmental differences, e.g. pH, lysed cells, inflammatory stimuli and metabolites, may determine in vivo the degree of accumulation.

The cellular association of sodium salicylate and indomethacin in peritoneal fluid of ascites bearing mice

The degree of association of sodium salicylate and indomethacin with inflammatory cells was measured under in vivo conditions in ascites bearing mice. These animals had sufficient volume of inflammatory effusion in the peritoneal cavity which enabled measurement of drug concentrations extravascularly, both in the effusion and in the inflammatory cells. A single anti-inflammatory dose of 200 mg/kg sodium salicylate or 10 mg/kg indomethacin was administered orally or intraperitoneally. The peritoneal salicylate levels exceeded blood levels starting approximately 4 h following oral drug application. Indomethacin peritoneal levels were substantially lower within 6 h after oral drug intake and exceeded the blood levels at 24 h. Intraperitoneal dosing of salicylate resulted after approximately 4 h in similar vascular and extravascular drug concentrations. Indomethacin was slowly cleared from the peritoneal compartment after intraperitoneal administration. Salicylate and indomethacin accumulated under in vivo inflammatory conditions in peritoneal cells. The degree of accumulation (the intracellular concentration was at most 6 times the extracellular concentration) was dependent on compound, time of sampling, protein binding and administration route. These results were confirmed in in vitro cell association experiments. Protein appeared to affect the macro- and micropartition of these drugs. The differences in biodistribution at macro level (tissue distribution) and at micro level (cellular association) between sodium salicylate and indomethacin were sought in the apparent disparities in protein binding and affinity for protein in mouse serum and exudate.

Classical absorption theory and the development of gastric mucosal damage associated with the non-steroidal anti-inflammatory drugs

Evidence has accumulated during the last decade to support the view that the pharmacokinetic behaviour of non-steroidal anti-inflammatory drugs (NSAIDs) contributes not only decisively to their therapeutic effects but also to the type and incidence of their side effects. It has been shown that NSAIDs reach particularly high concentrations in those compartments in which they cause effects and side effects. Specifically, the data reviewed herein indicate that the accumulation of NSAID within gastric mucosal cells a priori is a principal factor associated with the intervention of intracellular biochemical events and resultant gastric mucosal damage. To a large extent this behaviour is according to the precepts of classical absorption theory; in this respect the limitations of such theory are examined. Our survey further indicates that the failure of certain NSAIDs to significantly reduce gastric mucosal levels of prostaglandins (PG) in vivo may reflect pharmacokinetic differences between NSAIDs rather than tissue-specific differences in their potency as inhibitors of cyclo-oxygenase.

Reduction of aspirin-induced ulcers by a new imidazoline anti-inflammatory agent

We have previously described the anti-inflammatory and low ulcerogenic actions of the formamidine pesticide, chlordimeform (CDM). In this study, the related basic compound, CDMI [2-(2-methyl-4-chlorophenylamino)-2-imidazoline], also demonstrated potent anti-edema (vs. carrageenin) and low ulcerogenic activity. A nonulcerogenic i.p. dose of CDMI reduced aspirin (ASA)-induced ulcers [lesion index (L.I.): 25.8 for ASA alond vs. 5.3 for ASA + i.p. CDMI]; prevented stress-induced ulcers in mice; and decreased acid secretion (by 90% in the Shay rat preparation). A mildly ulcerogenic oral dose (0.6 mmol/kg) of CDMI prevented stress ulcers, but did not reduce ASA ulcers. A nonulcerogenic oral dose (0.15 mmol/kg) of CDMI did reduce ASA ulcers (L.I.: 24.5 for ASA alone vs. 14.7 for ASA + oral CDMI). Thus, CDMI is a unique anti-inflammatory agent with additional anti-secretory and ulcer-reducing actions.

Inhibition of anti-inflammatory drugs of prostaglandin production in cultured macrophages

1. A sensitive, simple, reproducible, and economical assay for structure-activity investigations of non-steroidal anti-inflammatory drugs (NSAID) is lacking. This has prompted us to investigate the advantages and limitations of defining for that purpose the potency of NSAID's as inhibitors of tumour promoter-induced prostaglandin (PG) release from mouse peritoneal macrophages in culture. 2. These cells release mainly PGE2 and PGI2 (measured as its stable hydrolysis product 6-keto-PGF1 alpha) upon stimulation with the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). 3. The PG release was dose-dependently inhibited by a variety of NSAID's. Their inhibitory potency was dependent on the culture conditions employed. The widely used acidic NSAID's were more potent when assayed under serum free culture conditions at low pH. 4. Dose response curves for acidic NSAID tested under serum free conditions allowed for the definition of IC50 values being reproducible within their 95% confidence limits. 5. The IC50 values obtained for different standard acidic NSAID's varied within 4 orders of magnitude. They corresponded favourably to their clinical potency and their potency in a variety of standard tests for anti-inflammatory drugs. 6. IC50 values of five congeners of indomethacin differed up to 2 orders of magnitude in agreement with in vivo observations indicating the applicability of this assay for structure-activity investigations.

Biodistribution of mild analgesics

1 Macro-autoradiographic methods were used to assess the biodistribution of [3H]-, or [14C]-acidic (aspirin, indomethacin, phenylbutazone) and non-acidic (antipyrine, aminopyrine, paracetamol) mild analgesics in rats with carrageenan-induced inflammation. 2 At anti-inflammatory doses all the acidic drugs (and/or their metabolites) were found to reach high concentrations in the stomach wall, liver, blood and bone marrow, kidney cortex and the inflamed tissue, that is, the tissues in which these drugs exert their therapeutic or side-effects. 3 In contrast, at analgesic doses, the non-acidic mild analgesics (and/or their metabolites) are equally distributed throughout the body with the exception of the gastro-intestinal lumen and the liver. This distribution pattern correlates well with the lack of acute side-effects and anti-inflammatory action of these drugs at therapeutic doses.

Prostaglandin release from macrophages: an assay system for anti-inflammatory drugs in vitro

It is the intention of this communication to present a simple and reliable in vitro system for the evaluation of anti-inflammatory drugs. The system described appears to combine the advantages of two established procedures, i.e. measurement of the inhibition of prostaglandin (PG) synthesis in vitro using microsomal enzyme preparations and the measurement of the inhibitory effects of drugs on PG synthesis in vivo avoiding major limitations. We propose to measure the effect of drugs on the PG release from mouse peritoneal macrophages in vitro. The influence of culture conditions, phagocytosis and drugs on the PG release from these cells is described. We found that antibody-coated erythrocytes are especially suitable triggers of PG release, and that the release can be inhibited by steroidal and non-steroidal anti-inflammatory drugs in concentrations resembling their effective doses in vivo.