Bioavailability studies with etodolac in dogs and man

Effects of flunixin meglumine or etodolac treatment on mucosal recovery of equine jejunum after ischemia

OBJECTIVE

To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion.

ANIMALS

24 horses.

PROCEDURE

Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithelial flux of tritium-labeled mannitol measured mucosal permeability. Denuded villous surface area and mean epithelial neutrophil count per mm2 were calculated. Western blot analysis for cyclooxygenase (COX)-1 and -2 was performed. Pharmacokinetics of flunixin and etodolac and eicosanoid concentrations were determined.

RESULTS

Ischemic-injured tissue from horses treated with flunixin and etodolac had significantly lower TER and increased permeability to mannitol, compared with that from horses treated with saline solution. Epithelial denudation after ischemia and 18 hours after recovery was not significantly different among treatments. Both COX-1 and -2 were expressed in ischemic-injured and nonischemic tissues. Ischemia caused significant upregulation of both COX isoforms. Eicosanoid concentrations were significantly lower in tissues from flunixin and etodolac-treated horses, compared with that from horses treated with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin and etodolac treatment retarded recovery of intestinal barrier function in jejunal mucosa after 18 hours of reperfusion, whereas tissues from horses treated with saline solution recovered baseline values of TER and permeability to mannitol.

Effect of carprofen, etodolac, meloxicam, or butorphanol in dogs with induced acute synovitis

OBJECTIVE

To compare the analgesic and anti-inflammatory effect of single doses of carprofen, etodolac, meloxicam, and butorphanol in dogs with induced acute synovitis (acute pain model) via kinetic gait analysis and orthopedic evaluation and examine measurement of serum C-reactive protein (CRP) concentration as an indicator of treatment efficacy.

ANIMALS

12 Beagles and 6 additional Beagles that were used only in serum CRP analyses.

PROCEDURE

Acute synovitis was induced in right stifle joints of dogs via intra-articular injection of monosodium urate solution. Treatments included butorphanol (0.2 mg/kg, i.v.), carprofen (4 mg/kg, PO), etodolac (17 mg/kg, PO), or meloxicam (0.2 mg/kg, PO); control dogs received no treatment. The procedure was repeated (3-week intervals) until all dogs received all treatments including control treatment. Lameness was assessed on a biomechanical force platform and via orthopedic evaluations of the stifle joints; blood was collected to monitor serum CRP concentration.

RESULTS

Compared with control dogs, treated dogs had significantly different vertical ground reaction forces and weight-bearing scores. Greatest improvement in lameness was observed in carprofen-treated dogs. Etodolac had the fastest onset of action. Compared with butorphanol treatment, only carprofen and etodolac were associated with significantly lower pain scores. An increase in serum CRP concentration was detected after intra-articular injection in all dogs; this change was similar among groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen, etodolac, and meloxicam had greater efficacy than butorphanol in relief of acute pain. Carprofen was most effective overall. In this acute pain model, serum CRP analysis was not useful to assess drug efficacy.

Simultaneous analysis of 14 non-steroidal anti-inflammatory drugs in human serum by electrospray ionization-tandem mass spectrometry without chromatography

A method is described for the simultaneous analysis of 14 non-steroidal anti-inflammatory drugs (NSAIDS) in human serum using negative electrospray ionization-tandem mass spectrometry (ESI-MS/MS). After addition of internal standard and protein precipitation using acetonitrile, samples were transferred to autosampler vials for direct analysis without chromatography. Injection of an air bubble with the sample and a multiple reaction monitoring (MRM) method using argon collision-induced dissociation (CID) of analyte (M-H)- ions permitted integration of the product ion peak areas to produce reproducible quantitative data over the range of concentrations expected in serum during routine use of these drugs. The method permitted the analysis of 30 samples per hour. Two hundred fifty consecutive analyses did not adversely affect instrument sensitivity.

Nonsteroidal anti-inflammatory drugs and corticosteroids for the management of canine osteoarthritis

Anti-inflammatory medications have long been prescribed for relief of the pain and discomfort associated with OA. This occurs despite the recognized side effects associated with use of NSAIDs and corticosteroids. Available evidence suggests that NSAIDs provide this relief through a combination of central and peripheral actions. Recent discovery of two isoforms of cyclooxygenase has increased our understanding of NSAID activity and may result in identification of drugs that potentially will have fewer side effects. A review of NSAIDs used in veterinary medicine indicates that relatively little is known regarding their role in treating OA, although controlled studies involving carprofen and etodolac have increased our knowledge of the efficacy of specific NSAIDs used for this purpose.

Gas chromatography-mass spectrometry determination of etodolac in human plasma following single epicutaneous administration

A highly sensitive gas chromatographic-mass spectrometric method for the determination of etodolac acid, as methyl ester, in plasma was developed. The feasibility and specificity of the method was ascertained monitoring the concentration levels in plasma samples collected from 12 male healthy volunteers given epicutaneously 5 g of 10% etodolac gel formulation.

Etodolac clinical pharmacokinetics

Etodolac is a chiral nonsteroidal anti-inflammatory drug (NSAID) that is marked as the racemate. Currently, the drug is available in several countries for the treatment of arthritis and the alleviation of pain. Etodolac possesses several unique disposition features mainly due to its stereoselective pharmacokinetics. In plasma, the concentrations of the 'inactive' R-enantiomer are about 10-fold higher than those of the active S-enantiomer, an observation that is novel among the chiral NSAIDs. In common with other NSAIDs, the drug is highly plasma protein bound, and undergoes virtually complete biotransformation to oxidised metabolites and acyl-glucuronides. Etodolac is well absorbed, with maximal plasma concentrations attained within 1 to 2 hours in healthy volunteers. The area under the plasma concentration-time curve of racemic etodolac increases linearly with doses used clinically. The elimination half-life of etodolac is between 6 and 8 hours in plasma, and is similar for both enantiomers. The volume of distribution (Vd) of racemic etodolac is higher than that of most other NSAIDs mainly because of the extensive distribution of the S-enantiomer. The very large Vd of the S-enantiomer, compared with its antipode is, at least in part, due to its less extensive plasma protein binding. In addition to the unchanged drug, substantial concentrations of the acyl-glucuronides of etodolac are found in both plasma and the synovial fluid of patients with arthritis. A limited amount of conjugated etodolac is found in the bile of patients following cholecystectomy. Hepatic cirrhosis has no effect on the pharmacokinetics of racemic etodolac, although the effect of hepatic dysfunction on the pharmacokinetics of the individual enantiomers has yet to be determined. In elderly non-arthritic individuals with excellent kidney function, aging does not affect the pharmacokinetics of etodolac. The pharmacokinetics of the drug in patients with renal failure have not been published, and may be important because the acyl-glucuronides are renally cleared.

Bioavailability and bioequivalence of two formulations of etodolac (tablets and suppositories)

We studied the influence of administration route on the biopharmaceutical behavior of etodolac. The levels obtained in plasma when the same dose of etodolac is administered orally (tablets, dosage form A) and rectally (suppositories, dosage form B) were compared. The study was done in a crossover design with healthy volunteers of both sexes, of average build, and younger than 35 years of age. From the concentration in plasma-time data, the maximum concentration in plasma (Cmax), time to Cmax, and area under the curve up to the last measurable concentration (AUC0t) or infinity (AUC 0 infinity) were calculated and compared by analysis of variance. With the exception of Cmax, no significant differences between treatments were found in the rest of the parameters. Finally, with formulation A (tablets) as a reference, the relative bioavailability was established, on the basis of the ratio (B:A) of AUC0t and AUC 9 infinity, within the range 100 +/- 20%. The results indicate that the two routes of administration are bioequivalent and that the rectal route is an alternative administration route for etodolac.

The stereoselective pharmacokinetics of etodolac in young and elderly subjects, and after cholecystectomy

The pharmacokinetics of the enantiomers of etodolac were studied in six young subjects (ages 28 +/- 3.3 years), 6 nonarthritic elderly subjects (ages 73 +/- 6.0 years), and in three cholecystectomy patients after single oral doses of the racemate (200 mg). In all subjects, the plasma concentrations of R-etodolac, which is pharmacologically inactive, greatly exceeded those of the pharmacologically active S-enantiomer. Stereoselectivity was reflected in the pharmacokinetics, with R > S for maximum peak plasma concentration and area under the concentration versus time curve, and S > R for apparent oral clearance and apparent volume of distribution. On average, less than 25% of the dose of each enantiomer was excreted in the urine within 24 hours as alkali-labile conjugates; little or no unchanged drug was recovered. Bile constituted a minor route of elimination of etodolac as conjugated enantiomers. There were no significant differences in the pharmacokinetics of etodolac enantiomers between the young and elderly subjects. The results reflect the importance of considering stereoselectivity in evaluating the pharmacokinetics of etodolac.

Etodolac. A reappraisal of its pharmacology and therapeutic use in rheumatic diseases and pain states

Etodolac is a nonsteroidal anti-inflammatory drug (NSAID) effective in the treatment of rheumatoid arthritis, osteoarthritis and ankylosing spondylitis, and in the alleviation of postoperative pain. Etodolac also provides relief of other types of pain, including that arising from gouty conditions and traumatic injury. In all indications, etodolac appears to be at least as effective as other NSAIDs. The incidence of clinical adverse effects other than abdominal pain and dyspepsia is similar to that observed with placebo, and etodolac has been associated with a low rate of gastrointestinal ulceration and other serious events. Data from preliminary animal studies have suggested that etodolac may provide more selective inhibition of prostaglandin synthesis at sites of inflammation than some other currently available NSAIDs. Thus, available evidence indicates that etodolac, with its low incidence of gastrointestinal events, is an effective and well tolerated alternative to other NSAIDs in the treatment of arthritic diseases and pain of various aetiologies and should be considered a first-line therapy.

Theoretical mechanism for the gastrointestinal safety of etodolac: selective sparing of cytoprotective prostaglandins

The high concentrations of pro-inflammatory prostaglandins (PGs) produced in the joint during the initial stage of inflammation can be decreased by inhibiting their biosynthesis with nonsteroidal anti-inflammatory drugs (NSAIDs). The commonly encountered gastrointestinal intolerance in human subjects treated with NSAIDs is generally attributed to inhibition of PG synthesis in gastric mucosa, where the natural role of locally biosynthesized PGs is to protect the mucosa from necrosis upon exposure to noxious agents. The action of an ideal NSAID should therefore be tissue specific, i.e., it should inhibit PG formation at the sites of inflammation but not in gastric mucosa, where PGs are needed for cytoprotection. We believe that etodolac, a new, structurally distinct NSAID, meets this criterion, inhibiting PG synthesis in a tissue-specific fashion. Experimental data supporting this interpretation were obtained in rats by demonstrating that daily administration of orally effective anti-inflammatory doses of etodolac had no significant effect on gastric mucosal PGE2 or prostacyclin levels (measured as the stable metabolite, 6-keto-PGF1 alpha). In contrast, naproxen, piroxicam, and aspirin caused a statistically significant PG depletion. The results obtained in rats thus support the view that the favorable gastrointestinal safety profile of etodolac in human patients may be attributable to selective sparing of the cytoprotective PGs in gastric mucosa.

Profile of etodolac: pharmacokinetic evaluation in special populations

The pharmacokinetics of etodolac, a new nonsteroidal anti-inflammatory drug, were compared in normal subjects, in patients with renal and hepatic disease, and in elderly patients. In 28 normal subjects, orally administered etodolac was rapidly absorbed. By 1.2 hours after ingestion of a 200 mg dose, the maximum serum concentration (Cmax) averaged 15.9 micrograms/ml, with more than 99% of the drug bound to serum protein. Clearance was primarily hepatic. The mean half-life (t1/2) was 6 to 7 hours. There were no apparent differences in Cmax, the time at which Cmax occurred (tmax), area under the serum concentration/time curve (AUC0-24), or t1/2 between groups of young men (n = 20), elderly men (n = 24), and elderly men with osteoarthritis (n = 20), after a single dose of etodolac or after 7 days of subchronic administration. Moreover there was no evidence of accumulation. There also were no differences in Cmax, tmax, AUC0-24 or t1/2 between groups of normal subjects (n = 10) and patients with mild-to-moderate renal impairment (n = 10). Patients with end-stage renal disease who were receiving chronic hemodialysis had the same mean serum concentration of free drug as normal subjects, even though mean serum levels of protein-bound etodolac were slightly lower than those in the normal subjects. The only significant (p less than 0.05) difference between patients with stable hepatic cirrhosis and normal, age-matched subjects was a slightly shorter tmax in the cirrhotic subjects (1.1 vs. 1.4 hours). These findings suggest that no alteration of etodolac dosage would be necessary in these high-risk groups.

The effect of cigarette smoke on gastroduodenal mucosal endogenous prostacyclin level (experimental and clinical observations)

In our opinion the endogenous prostacyclin (PGI2) is one of the most important natural protective substances in the gastric mucosa. We have, therefore checked in experimental circumstances in rats, as well as in clinical observations in humans, the possible effect of smoking on endogenous gastroduodenal mucosal PGI2 level. The animal experiments seem to verify that cigarette smoke really has an unwanted effect on the gastric mucosa. The target of this action is the endogenous PGI2 content of the mucosa. According to our observations in humans there is a definite tendency toward decreased endogenous PGI2 production in the gastroduodenal mucosa of smokers too.

Etodolac. A preliminary review of its pharmacodynamic activity and therapeutic use

Etodolac is a new non-steroidal agent (NSAID) with anti-inflammatory and analgesic activity. It has been studied in rheumatoid arthritis, osteoarthritis, and pain resulting from minor surgery. In the latter setting, etodolac is at least as effective as aspirin in terms of overall pain relief, and the duration of analgesic effect of a dose of 200 to 400mg is longer than that of aspirin. In rheumatoid arthritis, etodolac, administered twice daily, appears comparable in efficacy to moderate doses of aspirin (3 to 4g daily), but is better tolerated. To date, etodolac has not been compared clinically with analgesics other than aspirin and sulindac. As with other non-steroidal agents, gastrointestinal complaints are the most frequently reported side effects, but the incidence of most gastrointestinal effects was only slightly higher than with placebo. Thus, from studies in small numbers of patients etodolac appears at least as effective as aspirin and better tolerated. The relatively low incidence of gastrointestinal side effects in these studies awaits confirmation in well designed comparisons with widely used NSAIDs.

Disposition and biotransformation of 14C-etodolac in man

Four human subjects were given a capsule containing 200 mg of 14C-etodolac. At the peak (two hours after dosing), most of the radioactivity in serum was due to etodolac; subsequently, metabolites gradually appeared. The elimination half-life of etodolac from serum averaged six hours. Etodolac was greater than 99% bound to human serum proteins. An average of 73% of the dose was excreted in the urine and 14% in faeces within seven days, with 61% appearing in the urine during the first 24 h. Microbial transformation of etodolac was employed to biosynthesize sufficient amounts of two urinary metabolites to facilitate structure elucidation. Five metabolites, representing 65% of the radioactivity in urine collected 0-24 h after dosing (61% of the dose was excreted in urine within 24 h), were isolated and characterized by t.l.c., g.c., h.p.l.c., n.m.r (1H and 13C) and m.s. Most of the identified urinary components were conjugates of etodolac and three hydroxylated metabolites (6-hydroxyetodolac, 7-hydroxyetodolac and 8-(1-hydroxyethyl)etodolac). Two metabolites were identified as glucuronyl ester conjugates of etodolac and 7-hydroxyetodolac; the former represented about 20% of the urinary radioactivity. False positive tests for bilirubin in urine of patients treated with etodolac were found to be due to the two phenolic metabolites.

A review of selected investigational nonsteroidal antiinflammatory drugs of the 1980s

We reviewed the literature on 7 investigational nonsteroidal antiinflammatory drugs (NSAIDs): fenbufen, flurbiprofen, tiaprofenic acid, diclofenac, fenclofenac, etodolac and proquazone. These drugs all appear to be at least as effective as currently marketed NSAIDs. Toxicity reported with these newer agents is similar to that seen with other drugs in this class, with gastrointestinal complaints being most commonly reported. The frequency of gastritis and the extent of gastrointestinal microbleeding are less than what occur with aspirin therapy. Fenclofenac may affect thyroid function tests, an effect not noted with other NSAIDs. Proquazone and fenclofenac may have some effect on immunologic function similar to those of slow-acting antirheumatic drugs. These drugs decrease immunoglobulins, rheumatoid factor and C-reactive protein. The place for these drugs in the management of rheumatic diseases has yet to be defined. They may prove to be more beneficial than currently marketed drugs for some patients.