The effect of misoprostol on aspirin-induced gastroduodenal lesions in dogs

Gastric or duodenal perforation and secondary septic peritonitis following therapeutic nonsteroidal anti-inflammatory drug administration

OBJECTIVE

To report which nonsteroidal anti-inflammatory drugs (NSAIDs) were associated with gastric or duodenal perforation (GDP) in dogs presented to a university teaching hospital and to report the frequency of prescription of NSAIDs by the corresponding referring veterinary community during the same time period.

DESIGN

Retrospective cohort study of dogs from January 2007 to March 2020.

SETTING

Single university teaching hospital.

ANIMALS

A total of 30 dogs met inclusion criteria.

MEASUREMENTS AND MAIN RESULTS

Four dogs were administered more than 1 NSAID within 7 days of GDP, 3 dogs received a combination of an NSAID and a corticosteroid, and 1 dog received 2 NSAIDs and a corticosteroid. Four dogs received an overdose of an NSAID. One dog received an overdose of 1 NSAID and received an additional NSAID at the labeled dose within 7 days of GDP. Eighteen dogs received only 1 NSAID at the labeled dose. In these 18 dogs, meloxicam was administered in 44.4% (8/18), firocoxib in 27.8% (5/18), deracoxib in 16.7% (3/18), and piroxicam in 11.1% (2/18). One hundred and sixty surveys on NSAID prescribing practice were returned. Carprofen was the most commonly prescribed NSAID (70.6%), followed by meloxicam (10.6%), deracoxib (8.4%), firocoxib (7.8%), aspirin (1.5%), and other (0.9%).

CONCLUSIONS

NSAID administration, even at labeled doses, appears to be a precipitating factor for GDP. Despite carprofen being the most frequently prescribed NSAID over the study period, no case of GDP received it as a single therapeutic agent. Further prospective evaluation is needed to verify these findings.

Gastroduodenal ulceration in dogs with liver disease

Background

Liver disease is frequently cited as a cause of gastroduodenal ulceration (GDU) in dogs but studies regarding GDU and liver disease are limited.

Objectives

To document the presence of GDU in dogs with liver disease.

Animals

Forty dogs that underwent liver biopsy, computed tomographic (CT) angiography or both at the University of Florida Small Animal Hospital to diagnose congenital or acquired liver disease.

Methods

Cross‐sectional study. Dogs had gastroduodenoscopy performed with photographic and video documentation in a standardized fashion. Lesions (hemorrhage, erosions, ulcers) in the esophagus, stomach, and duodenum were scored based on a grading scale. Presence of esophageal varices was recorded. Dogs were categorized into 4 groups according to cause of liver disease (inflammatory disease, cirrhosis, congenital, other). Presence or absence of ulcers, erosions or both as well as total endoscopic scores were compared among groups.

Results

Forty dogs were enrolled with the following distribution: 13 congenital, 13 inflammatory, 3 cirrhosis, and 11 other. Four dogs had GDU (10%; 95% confidence interval [CI], 3%‐24%) and 6 dogs had erosions (15%; 95% CI, 6%‐30%). No difference was found in total endoscopic score (P = .21) or in the proportion of dogs with ulcers, erosions or both versus those without (P = .25) among the groups.

Conclusions and Clinical Importance

Gastroduodenal ulceration was found in 10% of dogs with liver disease in this population. Additional studies are warranted to confirm these findings in larger numbers of dogs with specific disease etiologies.

Effects of Aspirin and Prednisone on Platelet Function and Thromboxane Synthesis in Healthy Dogs

Glucocorticoid administration is a risk factor for thromboembolism in hypercoagulable dogs, and it is unknown if aspirin counteracts glucocorticoid-induced hypercoagulability. The objective was to determine the effects of sustained aspirin and prednisone administration on platelet function and thromboxane synthesis. Our hypothesis was that aspirin would consistently inhibit platelet function and thromboxane synthesis when administered with or without prednisone. In 24 healthy dogs, platelet aggregometry and urine 11-dehydro-thromboxane-B₂ (11-dTXB₂)-to-creatinine ratios were measured on days 0, 14, and 28. Dogs were administered placebos, aspirin (2 mg/kg/d), prednisone (2 mg/kg/d), or prednisone/aspirin combination therapy PO for 28 days in a randomized double-blinded study. Aspirin response was based on a >25% reduction in platelet aggregation compared to pre-treatment values. Results were compared using mixed model, split-plot repeated measures ANOVAs. P < 0.05 was considered significant. AUC differed significantly by time [F_(2,40) = 10.2, P < 0.001] but not treatment or treatment-by-time. On day 14, 2 dogs were aspirin responders (aspirin, 1; placebo, 1). On day 28, 3 dogs were aspirin responders (aspirin, 2; prednisone/aspirin, 1). Urine 11-dTXB₂-to-creatinine ratios differed significantly by group [F_(3,20) = 3.9, P = 0.024] and time [F_(2,40) = 8.7, P < 0.001), but not treatment-by-time. Post-hoc analysis revealed significant differences between aspirin and placebo groups (P=0.008), aspirin and prednisone/aspirin groups (P = 0.030), and placebo and prednisone groups (P = 0.030). In healthy dogs, sustained aspirin, prednisone, and combination therapy do not inhibit platelet aggregation, and when used as individual therapies, aspirin and prednisone decreased thromboxane synthesis. Additional studies using varied platelet function methodologies in hypercoagulable dogs are necessary.

ACVIM consensus statement: Support for rational administration of gastrointestinal protectants to dogs and cats

The gastrointestinal (GI) mucosal barrier is continuously exposed to noxious toxins, reactive oxygen species, microbes, and drugs, leading to the development of inflammatory, erosive, and ultimately ulcerative lesions. This report offers a consensus opinion on the rational administration of GI protectants to dogs and cats, with an emphasis on proton pump inhibitors (PPIs), histamine type-2 receptor antagonists (H2 RAs), misoprostol, and sucralfate. These medications decrease gastric acidity or promote mucosal protective mechanisms, transforming the management of dyspepsia, peptic ulceration, and gastroesophageal reflux disease. In contrast to guidelines that have been established in people for the optimal treatment of gastroduodenal ulcers and gastroesophageal reflux disease, effective clinical dosages of antisecretory drugs have not been well established in the dog and cat to date. Similar to the situation in human medicine, practice of inappropriate prescription of acid suppressants is also commonplace in veterinary medicine. This report challenges the dogma and clinical practice of administering GI protectants for the routine management of gastritis, pancreatitis, hepatic disease, and renal disease in dogs and cats lacking additional risk factors for ulceration or concerns for GI bleeding. Judicious use of acid suppressants is warranted considering recent studies that have documented adverse effects of long-term supplementation of PPIs in people and animals.

Gastroprotectants in small animal veterinary practice - a review of the evidence. Part 1: cyto-protective drugs

Diverse drugs with presumed cytoprotective effect have been used therapeutically in small animal veterinary practice for various gastro-intestinal conditions such as oesophagitis, gastric ulceration, gastritis or chronic gastro-enteropathies. Their efficacy has been doubted in human medicine, raising similar questions in the veterinary field. The aim of this review was to assess the current evidence on the efficacy and safety of these drugs in dogs and cats. Through a systematic review of the literature, we identified 37 articles on the use of misoprostol, sucralfate and other gastroprotectants in dogs and cats. There was evidence to support use of misoprostol in the prevention of aspirin-induced gastroduodenal mucosal injury in dogs, and for use of sucralfate in the prevention of acid-induced oesophagitis in cats. However, the overall quality of evidence supporting the use of these drugs in small animal patients was poor. In contrast, there was evidence of important adverse effects, especially drug interaction and gastro-intestinal signs. We therefore recommend prescribing these drugs with caution until further well-conducted studies reveal a useful gastroprotectant effect.

Mechanisms of injury and emergency care of acute spinal cord injury in dogs and cats

OBJECTIVES

To review the literature in regards to the pathophysiology of acute spinal cord injury, and to describe current concepts in regards to patient assessment, diagnostic, and therapeutic measures with a special emphasis on emergency and critical care considerations.

ETIOLOGY

Acute spinal cord injury occurs in 2 phases. The primary injury occurs at the time of initial injury and may include intervertebral disk herniation, vertebral fracture or luxation, penetrating injury, and vascular anomalies such as fibrocartilaginous embolic myelopathy. Secondary injury occurs following primary injury and is multifactorial encompassing numerous biochemical and vascular events that result in progression of injury.

DIAGNOSIS

The diagnosis is based on history and physical examination findings. A neurologic examination should be performed following initial patient assessment and stabilization. Further diagnostics to characterize acute spinal injury include radiographs and advanced imaging modalities such as myelography, computed tomography, or magnetic resonance imaging.

THERAPY

Initial treatment should focus on addressing the patient's cardiovascular and respiratory system. Supportive measures to support systemic perfusion are vital to minimizing secondary injury. Specific therapy toward minimizing secondary injury in veterinary medicine remains controversial, especially in regards to the utilization of methylprednisolone. Other therapies are either in need of additional research or have failed to document clinical difference.

PROGNOSIS

The prognosis for acute spinal injury is varied and is dependent upon the presence of concurrent trauma, location, and type of primary injury sustained, and extent of neurologic impairment at the time of initial presentation. The etiology of the underlying trauma is of great importance in determining prognosis and outcome. Loss of deep pain is generally accepted as a poor prognostic indicator; however, even these patients can recover depending on their response to treatment.

Lyophilized aspirin with trehalose may decrease the incidence of gastric injuries in healthy dogs

Trehalose has several novel anti-inflammatory and cell-protective functions. We hypothesized that lyophilized aspirin/trehalose could decrease the severity of aspirin-induced gastropathy. Thirteen dogs were assigned into aspirin, lyophilized aspirin/trehalose, and control groups, and the gastric lesions were assessed on gastroscopy with the modified Lanza scale. Another 6 dogs were used to measure the plasma aspirin concentration by high-performance liquid chromatography after aspirin or lyophilized aspirin/trehalose administration. The results indicated that lyophilized aspirin/trehalose induced less gastric ulceration than aspirin despite maintaining therapeutic concentrations of plasma aspirin in both the groups. Lyophilized aspirin/trehalose might be a solution to decrease aspirin-induced gastropathy.

Effects of zinc-L-carnosine and vitamin E on aspirin-induced gastroduodenal injury in dogs

BACKGROUND

Nonsteroidal anti-inflammatory drugs frequently cause gastrointestinal (GI) injury. Zinc-L-carnosine has antioxidant, anti-inflammatory, mucosal protective, and healing properties in rodent models and in some human studies of GI injury.

HYPOTHESIS

The combination of zinc-L-carnosine and vitamin E attenuates aspirin-induced gastroduodenal mucosal injury.

ANIMALS

Eighteen healthy random-source Foxhound dogs.

METHODS

In this randomized, double-blinded, placebo-controlled study dogs were treated with placebo (n = 6; 0X group), 30 mg/30 IU (n = 6; 1X group), or 60 mg/60 IU (n = 6; 2X group) zinc-L-carnosine/vitamin E orally every 12 hours for 35 days. Between Day 7 and 35, GI mucosal lesions were induced with aspirin (25 mg/kg p.o. q8h). Mucosal injury lesions (hemorrhage, erosion, and ulcer) were assessed by gastroduodenoscopy on Days 14, 21, and 35 with a 12-point scoring scale.

RESULTS

At baseline (Day -1) gastroscopy scores were not significantly different between groups (mean ± SD: 0X, 4.4 ± 0.8; group 1X, 4.4 ± 0.6; group 2X, 4.2 ± 0.3; P= .55). Gastroscopy scores increased significantly in all groups between Day -1 and Days 14, 21, and 35 (P < .0001). On Day 35, gastroscopy scores were 29.2 ± 5.2 (0X), 27.3 ± 3.7 (1X), and 28.6 ± 3.3 (2X). Mean gastroscopy scores were not significantly different among treatment groups on any of the days (P = .61).

CONCLUSIONS AND CLINICAL IMPORTANCE

Administration of the combination of zinc-L-carnosine and vitamin E at 1X or 2X dosing did not attenuate aspirin-induced gastroduodenal mucosal injury.

Effects of prednisone alone or prednisone with ultralow-dose aspirin on the gastroduodenal mucosa of healthy dogs

BACKGROUND

The coadministration of prednisone and ultralow-dose aspirin has been recommended for the management of various diseases, but the safety of this combination in dogs has not been studied.

HYPOTHESES

The gastroduodenal lesions associated with prednisone and ultralow-dose aspirin administration will be similar to those caused by prednisone alone, but both treatments will result in more severe lesions than placebo.

ANIMALS

Eighteen healthy adult purpose-bred dogs.

METHODS

Randomized, blinded, placebo-controlled study of 3 treatment groups for 27 days: placebo, prednisone, and prednisone and aspirin. Gastroduodenoscopy was performed before and on days 5, 14, and 27 of treatment and mucosal lesions scores were assigned. Mucosal lesion scores were compared by a Kruskal-Wallis test. Clinical signs were compared by the Friedman's chi-square test (significance at P < .05).

RESULTS

There were no significant differences in the gastroduodenal lesion scores among groups, or within groups at any time during the study. Significantly more dog-days of diarrhea occurred in the prednisone and aspirin group during treatment, compared with baseline. No significant differences in clinical signs were found among any of the groups.

CONCLUSION

The concurrent use of prednisone and ultralow-dose aspirin did not increase the severity of gastroduodenal lesions compared with prednisone or placebo. Coadministration of prednisone and ultralow-dose aspirin increases the frequency of mild, self-limiting diarrhea in some dogs.

Cyclooxygenase expression and prostanoid production in pyloric and duodenal mucosae in dogs after administration of nonsteroidal anti-inflammatory drugs

OBJECTIVE

To assess cyclooxygenase (COX) expression and prostanoid concentrations in pyloric and duodenal mucosae of dogs after administration of nonsteroidal anti-inflammatory drugs (NSAIDs).

ANIMALS

8 healthy dogs.

PROCEDURES

Each dog received carprofen (4.4 mg/kg, q 24 h), deracoxib (2 mg/kg, q 24 h), aspirin (10 mg/kg, q 12 h), and placebo (1 dog treat, q 24 h) orally for 3 days (4-week interval between treatments). Before study commencement (baseline) and on day 3 of each treatment, pyloric and duodenal mucosal appearance was assessed endoscopically and biopsy specimens were obtained for histologic examination. Cyclooxygenase-1 and COX-2 protein expressions were assessed via western blotting, and prostanoid concentrations were measured via ELISAs. An ANOVA was used to analyze data.

RESULTS

Treatments had no effect on mucosal appearance and ulceration was not evident histologically. In pyloric and duodenal mucosae, COX-1 expression was unaffected by treatments. Cyclooxygenase-2 expression remained unchanged in pyloric mucosa; in duodenal mucosa, aspirin significantly increased COX-2 expression, compared with effects of deracoxib and carprofen. At baseline, total prostaglandin and thromboxane B2 concentrations in pyloric mucosa were significantly greater than those in duodenal mucosa. Aspirin significantly decreased both prostanoid concentrations in both mucosal tissues, compared with other treatments. In pyloric mucosa, carprofen administration significantly decreased total prostaglandin and thromboxane B2 concentrations, compared with deracoxib administration.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, prostanoid synthesis was greater in pyloric mucosa than it was in duodenal mucosa. Nonselective NSAIDs significantly decreased prostanoid concentrations in these mucosae, compared with the effects of a selective COX-2 NSAID.

Effects of cyclooxygenase inhibition on the gastrointestinal tract

Cyclooxygenase (COX) is a rate-limiting enzyme that catalyzes the conversion of arachidonic acid, an essential fatty acid present in cell membrane phospholipids and liberated by phospholipase, into prostaglandins (PGs) and prostanoids. COX has two distinct membrane-anchored isoenzymes; COX-1 and COX-2. COX-1 is a constitutively expressed and found in most normal body tissues; COX-2 is expressed in normal tissues at low levels and is highly induced by pro-inflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include: (1) conventional non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs); (2) selective COX-2 inhibitors (COXIBs); and (3) COX-1 inhibitors. Non-selective NSAIDs, at therapeutic doses, inhibit both COX-1 and COX-2. The anti-inflammatory benefits of these drugs are primarily derived from COX-2 inhibition, while inhibition of COX-1 often elicits gastrointestinal (GI) toxicity. Therefore, COXIBs were developed to provide a selective COX-2 agent, i.e., one, that at fully therapeutic doses demonstrated comparable therapeutic benefit to non-selective NSAIDs, without the attendant COX-1-mediated GI toxicities. In this review, we evaluate available literature describing the pathophysiologic role of cyclooxygenases and the effects of their inhibition in GI system in experimental and domestic animal species.

Multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine in the cat

The purpose of this study was to evaluate the multiple dose pharmacokinetics and acute safety of piroxicam and cimetidine alone and in combination in cats. Seven healthy cats were included in this randomized-crossover study. The cats were assigned to groups designated to receive cimetidine alone (15 mg/kg, p.o., q12 h), piroxicam alone (0.3 mg/kg, p.o., q24 h), and piroxicam combined with cimetidine (both at aforementioned doses). The cats were dosed for 10 days followed by at least a 2-week washout period between trials. Serial blood samples were collected following the first and last doses and analyzed utilizing a high-performance liquid chromatography with mass spectrometry detection (LC/MS) assay. Pharmacokinetic parameters were determined using noncompartmental analysis. Endoscopic evaluation of the gastric mucosa was performed and serum urea nitrogen (SUN), creatinine, alkaline phosphatase (ALP), and alanine transaminase (ALT) activities were evaluated. There were not a clinically relevant difference between the pharmacokinetic parameters of piroxicam administered alone or in combination with cimetidine after either the first or last dose. Gastric ulcers were not observed in any cats although gastric erosions were. The SUN, creatinine, ALP, and ALT activities remained within reference ranges for all cats. It appears that once daily, short-term use of piroxicam alone and in combination with cimetidine in cats is relatively safe based on the parameters evaluated in this study. However, further studies are necessary to determine the long-term gastrointestinal safety of piroxicam.

Endoscopic evaluation of the gastroduodenal mucosa to determine the safety of short-term concurrent administration of meloxicam and dexamethasone in healthy dogs

OBJECTIVE

To evaluate the safety, with respect to the development of gastric ulcers and erosions, of concurrent administration of meloxicam and dexamethasone for 3 days to healthy dogs.

ANIMALS

20 conditioned purpose-bred research Beagles.

PROCEDURE

Seven days prior to treatment, dogs were anesthetized for endoscopic evaluation of the upper portion of the gastrointestinal tract (ie, the gastric and duodenal mucosa). Five regions of the gastroduodenal area were scored by 2 investigators. Dogs were randomly assigned to 1 of 4 treatment groups as follows: saline-saline, dexamethasone-saline, saline-meloxicam, and dexamethasone-meloxicam groups. On days 1, 2, and 3, dogs received either dexamethasone or saline (0.9% NaCl) solution injections SC twice daily. On days 2, 3, and 4, dogs received either meloxicam or saline solution injections SC once daily. On day 2, dogs were anesthetized for a sham surgery (ie, electrostimulation). On day 5, the gastroduodenal area of each dog was reevaluated by use of endoscopic evaluation and histologic examination of biopsy specimens.

RESULTS

The total endoscopic score of the dexamethasone-meloxicam group was significantly greater than the scores of the other groups. The dexamethasone-saline group had a mean cumulative score that was significantly greater than the saline-meloxicam or saline-saline groups. Endoscopic scores of the saline-meloxicam group were not significantly different from scores of the saline-saline group. No significant differences in histologic findings were found between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In healthy dogs, meloxicam appears to be safe with regard to adverse effects on the gastrointestinal tract. Concurrent administration of dexamethasone and meloxicam is more likely to cause gastric erosions than meloxicam administration alone.

The effect of dosing interval on the efficacy of misoprostol in the prevention of aspirin-induced gastric injury

The effect of twice-daily administration of misoprostol on aspirin-induced gastric injury was evaluated. Twenty-four random-source dogs were divided into groups that received aspirin and misoprostol as follows: group I, aspirin 25 mg/kg PO q8h and placebo PO q8h; group II, aspirin 25 mg/kg PO q8h and misoprostol 3 microg/kg PO q8h; group III, aspirin 25 mg/kg PO q8h, misoprostol 3 microg/kg PO q12h, and placebo PO q24h; and group IV, aspirin 25 mg/kg PO q8h, misoprostol 3 microg/kg PO q24h, and placebo PO q12h for 28 days. Gastroscopy was performed on days -9, 5, 14, and 28. Visible lesions were scored on a scale of 1 (mucosal hemorrhage) to 11 (perforating ulcer). No difference in total score was identified between groups I and IV on any day. Median total scores for groups II and III were significantly (P < or = .05) lower compared to groups I and IV on day 5. Group III had a significantly lower score (P < or = .05) than groups I, II, and IV on day 28. This study suggests that misoprostol 3 microg/kg PO q12h is as effective as misoprostol 3 microg/kg PO q8h in preventing aspirin-induced gastric injury in this model. However, misoprostol 3 microg/ kg PO q8h was less effective in preventing aspirin-induced gastric injury on days 14 and 28 than in previous studies. No difference among numbers of dog-days of vomiting, diarrhea, or anorexia was detected among groups.

Oral medications

Many medications are available today by prescription or in over-the-counter preparations. This article reviews the pharmacokinetics, mechanism of action, toxicity, clinical signs, and management procedures necessary for some oral medications. The medications reviewed include selective serotonin reuptake inhibitors, benzodiazepines, amphetamines or amphetamine like drugs, carprofen, cyclooxygenase-2 inhibitors, pseudoephedrine, calcium channel blockers, and baclofen.

Pharmacologic considerations for opiate analgesic and nonsteroidal anti-inflammatory drugs

When administering opioid analgesic drugs or nonsteroidal anti-inflammatory drugs, veterinarians are often not familiar enough with the underlying pharmacology of the drugs, particularly with the potential for drug interactions and adverse effects. This article considers some of the pharmacologic features of these drugs and provides a basis for important interactions, contraindications, and adverse effects.

Management of cancer pain

Pain secondary to cancer in animals should be promptly addressed to alleviate suffering, stress, and anxiety and to improve quality of life. Uncontrolled cancer pain can have a negative effect on the owners and caregivers of affected animals. The pathophysiology of cancer pain is discussed in this article, along with pain evaluation and monitoring. Treatment of cancer pain should be individualized, and a step-wise approach to the management of cancer pain is presented. The use of opioids, nonsteroidal anti-inflammatory drugs, and adjuvant medications are also reviewed.

Gastrointestinal pharmacology

Diseases of the gastrointestinal tract that require pharmacologic management, usually in combination with other treatments, are gastric ulcers (omeprazole and others), colic (laxatives, analgesics), diarrhea (antibiotics, protectants and absorbents, glucocorticoids, motility inhibitors), reperfusion injury, postoperative ileus (prokinetic drugs), and adhesions. There is growing evidence that nonsteroidal anti-inflammatory drugs can alter important physiologic properties of the intestine; however, these drugs are valuable analgesics for horses and their use should be tempered with an awareness of their harmful effects. The role of antibiotics in treating gastrointestinal disease is controversial, but their ability to induce life-threatening diarrhea is well known and invites caution and defensible use of these drugs in horses.

Gastrointestinal drugs

Various drugs are commonly used for the many gastrointestinal problems that are routinely seen in dogs and cats. Many of these drugs are briefly reviewed in this article. Anecdotal as well as documented findings are provided that will hopefully allow the clinician to use them wisely and effectively in the many clinical situations that arise daily. Emetics, although not used for gastrointestinal problems, are also reviewed because of their obvious connection with the gastrointestinal tract.

Pain and its management

The management of pain in geriatric patients is a critical part of good veterinary care. The older patient poses unique issues in the selection of appropriate analgesic drugs due to altered drug absorption, metabolism and the frequent occurrence of underlying disease. Narcotics and NSAIDs are important analgesics that can be safely administered in geriatric patients provided that dosing amount and frequency are adjusted. Alternative analgesic techniques, such as nerve blocks, spinal analgesia and transcutaneous patches, offer a particularly useful source of analgesia in compromised geriatric patients.

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.

Principles of analgesic drug therapy

The drugs most often used for pain relief in animals are the nonsteroidal antiinflammatory drugs (NSAIDS) and the opioid analgesics. The NSAIDS are effective, inexpensive, and long-acting drugs, but their degree of analgesia is limited by the adverse effects at high doses. The most common adverse effect from NSAIDS is gastritis and gastrointestinal hemorrhage and ulceration. This is most common from high doses, or from using NSAIDS not appropriate for dogs such as ibuprofen or indomethacin. The NSAIDS used in dogs include aspirin, phenylbutazone, naproxen, piroxicam, ketoprofen, and carprofen. Carprofen is a new drug with a low incidence of side effects and its popularity is increasing at a fast rate. For more acute pain, especially acute pain from surgery or trauma, opioids are frequently administered. Opioids have the advantage of higher efficacy when the dose is increased. The incidence of adverse effects is low, but side effects of sedation are common. An important disadvantage of opioids is their short duration and low oral absorption, which necessitates a frequent injection or i.v. infusion for most patients. Recent studies have established other applications for administration of opioids such as a transdermal fentanyl patch. These applications offer new possibilities for convenient administration.