Pharmacokinetic/pharmacodynamic evaluation of grapiprant in a carrageenan-induced inflammatory pain model in the rabbit

Pharmacokinetics of a single oral dose of grapiprant in juvenile pigs (Sus scrofa domestica)

Both pet and research pigs can suffer from some degree of pain from surgery, injuries, or osteoarthritis (OA). Despite this, there is a paucity of data on safe and effective analgesia agents in pigs. Grapiprant is an EP4 antagonist that blocks the action of the pro-inflammatory prostanoid, PGE2 . It has shown efficacy in attenuating pain associated with ovariohysterectomy and OA in dogs. However, there are no data regarding grapiprant in pigs. Therefore, the pharmacokinetic profile of orally administered grapiprant to juvenile pigs (Sus scrofa domestica) was evaluated in this study. Seven juvenile pigs received 12 mg/kg grapiprant orally. Blood was collected from an indwelling jugular catheter using the push-pull method at set timepoints up to 48 hours. Sample analysis was performed with high-performance liquid chromatography. Mean grapiprant plasma concentration was 164.3 ± 104.7 ng/mL which occurred at 0.8 ± 0.3 h. This study demonstrated that grapiprant concentrations consistent with analgesia in dogs were reached at this dosage in pigs. Further studies are needed to evaluate the efficacy of grapiprant in pigs.

Treatment of Pain in Rabbits

Rabbits occupy facets of veterinary medicine spanning from companion mammals, wildlife medicine, zoologic species, and research models. Therefore, analgesia is required for a variety of conditions in rabbits and is a critical component of patient care. Considerations when selecting an analgesic protocol in rabbits include timing of administration, route of administration, degree or anticipated pain, ability to access or use controlled drugs, systemic health, and any potential side effects. This review focuses on pharmacologic and locoregional management of pain in rabbits and emphasizes the need for further studies on pain management in this species.

Quantification of Grapiprant and Its Stability Testing under Changing Environmental Conditions

Grapiprant is a new analgesic and anti-inflammatory drug belonging to the piprant class, approved in 2016 by the FDA Veterinary Medicine Center for the treatment of pain and inflammation associated with osteoarthritis in dogs. It acts as a highly selective antagonist of the EP4 receptor, one of the four prostaglandin E2 (PGE2) receptor subtypes. It has been shown to have anti-inflammatory effects in rat models of acute and chronic inflammation and clinical studies in people with osteoarthritis. The current state of knowledge suggests the possibility of using it in oncological therapy. The manuscript presents the development of conditions for the identification and quantitative determination of grapiprant by thin-layer chromatography with densitometric detection. The optimal separation of the substance occurs using silica gel 60F254 chromatographic plates and the mobile phase containing ethyl acetate-toluene-butylamine. Validation (according to ICH requirements) showed that the developed method is characterized by straightness of results in a wide concentration range with the limit of detection of 146.65 µg/mL. The %RSD values of the precision and accuracy confirm the sensitivity and reliability of the developed procedure. Next, the method was used for quantification of grapiprant in a pharmaceutical preparation, and for stability studies under various environmental conditions. Additionally, the mass studies were carried out on the stressed samples using the UPLC-MS/MS method. The degradation products were primarily characterized by comparing their mass fragmentation profiles with those of the drug. The results indicated a potential degradation pathway for grapiprant.

Grapiprant or carprofen following ovariohysterectomy in the cat: analgesic efficacy, hematological, biochemical and urinalysis evaluation

OBJECTIVES

This study aimed to compare the analgesic effect between carprofen and grapiprant every 12 or 24 h on postoperative pain in cats undergoing ovariohysterectomy, in addition to the effects on the hematological, biochemical and urinalysis variables.

METHODS

A total of 32 female cats were randomly divided into three groups, according to the treatment administered with the first dose given orally 90 mins before surgery, as follows: CAR (cats received 4 mg/kg carprofen, n = 11); GRA1 (cats received 2 mg/kg grapiprant, n = 10); and GRA2 (cats received 2 mg/kg grapiprant q12h, n = 11). Pain was assessed by UNESP-Botucatu Multidimensional Composite Pain Scale (UNESP) and Glasgow Feline Composite Measure Pain Scale (GLASGOW) for cats preoperatively (baseline) and at 1, 3, 6, 8, 12 and 24 h after extubation. Venous blood was collected at baseline, and 12 and 24 h after the administration of carprofen or grapiprant to perform a complete blood count (CBC), the percentage of Heinz bodies and serum biochemistry (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyltransferase, creatinine and urea). Urinalysis was performed at baseline and 24 h after extubation. Glucose levels were evaluated at baseline and 1 h postoperatively.

RESULTS

Pain scores were not significantly different among groups in both scales, although pain was higher at 3 h in comparison with 24 h in all groups. In the GRA1 and GRA2 groups, 67% (14/21) of cats needed rescue analgesia compared with 18% (2/11) in the CAR group. Glucose increased from baseline to 1 h in the GRA1 and GRA2 groups. None of the CBC, serum biochemistry and urinalysis variables differed among groups.

CONCLUSIONS AND RELEVANCE

Grapiprant did not promote adequate analgesia during the first 3 h postoperatively in cats undergoing ovariohysterectomy compared with carprofen, and no benefits were observed by administering grapiprant every 12 h.

Pharmacokinetics of grapiprant administered to red-tailed hawks (Buteo jamaicensis) after food was withheld for 24 hours

OBJECTIVE

To identify an oral dose of grapiprant for red-tailed hawks (RTHAs; Buteo jamaicensis) that would achieve a plasma concentration > 164 ng/mL, which is considered therapeutic for dogs with osteoarthritis.

ANIMALS

6 healthy adult RTHAs.

PROCEDURES

A preliminary study, in which grapiprant (4 mg/kg [n = 2], 11 mg/kg [2], or 45 mg/kg [2]) was delivered into the crop of RTHAs from which food had been withheld for 24 hours, was performed to obtained pharmacokinetic data for use with modeling software to simulate results for grapiprant doses of 20, 25, 30, 35, and 40 mg/kg. Simulation results directed our selection of the grapiprant dose administered to the RTHAs in a single-dose study. Plasma grapiprant concentration, body weight, and gastrointestinal signs of RTHAs were monitored.

RESULTS

On the basis of results from the preliminary study and simulations, a grapiprant dose of 30 mg/kg was used in the single-dose study. The geometric mean maximum observed plasma concentration of grapiprant was 3,184 ng/mL, time to maximum plasma grapiprant concentration was 2.0 hours, and the harmonic mean terminal half-life was 17.1 hours. No substantial adverse effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Although the single dose of grapiprant (30 mg/kg) delivered into the crop achieved plasma concentrations > 164 ng/mL in the RTHAs, it was unknown whether this concentration would be therapeutic for birds. Further research that incorporates multidose assessments, safety monitoring, and pharmacodynamic data collection is warranted on the use of grapiprant in RTHAs from which food was withheld versus not withheld.

Grapiprant: A snapshot of the current knowledge

Grapiprant is the pioneer member of the novel piprant class, a potent and specific antagonist of the prostaglandin E2 receptor 4. It has been approved in veterinary medicine for the control of pain and inflammation associated with osteoarthritis in dogs at the dose regimen of 2 mg/kg once a day by the FDA and EMA (for pain only) in 2016 and 2018, respectively. The aim of this narrative review was to report the analytical methods, pharmacokinetics, pharmacodynamics and safety of grapiprant in several animal species using the best available published scientific evidence. In conclusion, most of the analytical methods proposed for grapiprant detection are simple, reliable, sensitive and validated. The pharmacokinetics show discrepancies between animal species. The therapeutic efficacy seems more suited to chronic rather than acute pain.

Dietary Supplementation with Palmitoyl-Glucosamine Co-Micronized with Curcumin Relieves Osteoarthritis Pain and Benefits Joint Mobility

Simple Summary

Canine osteoarthritis is a chronic degenerative joint disease and a major cause of elective euthanasia. The disorder increasingly limits joint motion, might cause lameness as well as pain, and impacts quality of life. An unmet need remains for safe and effective therapies for osteoarthritis. Palmitoyl-glucosamine and curcumin are used in animal nutrition. A co-micronized formulation, with the two substances being jointly processed to reduce their particle size and increase the extent to which they can be absorbed, is currently available on the European market. The present study investigated if this formulation could relieve joint pain and benefit mobility. Two well-established rat models of inflammation and osteoarthritis pain were used. Results from the first set of experiments showed that the dietary supplement relieved experimentally induced paw edema, infiltration of inflammatory cells, and decreased sensitivity to painful stimuli (thermal hyperalgesia). In the osteoarthritis model, the supplement proved to protect joint cartilage against degradation and successfully address neuropathic pain (i.e., pain from normally non-painful stimuli). Locomotor function recovered by 45% under supplement administration. The present findings suggest that the dietary supplement with palmitoyl-glucosamine co-micronized with curcumin might help manage osteoarthritis.

Abstract

Chronic mixed pain and orthopedic dysfunction are the most frequently associated consequences of canine osteoarthritis (OA). An unmet need remains for safe and effective therapies for OA. Palmitoyl-glucosamine (PGA) and curcumin are safe and naturally occurring compounds whose use is limited by poor bioavailability. Micronization is an established technique to increase bioavailability. The aim of this study was to investigate if the dietary supplementation with PGA co-micronized with curcumin (PGA-Cur, 2:1 ratio by mass) could limit pathologic process in two well-established rat models of inflammation and OA pain, i.e., subplantar carrageenan (CAR) and knee injection of sodium monoiodoacetate (MIA), respectively. In CAR-injected animals, a single dose of PGA-cur significantly reduced paw edema and hyperalgesia, as well as tissue damage and neutrophil infiltration. The repeated administration of PGA-Cur three times per week for 21 days, starting the third day after MIA injection resulted in a significant anti-allodynic effect. Protection against cartilage damage and recovery of locomotor function by 45% were also recorded. Finally, PGA-cur significantly counteracted MIA-induced increase in serum levels of TNF-α, IL-1β, NGF, as well as metalloproteases 1, 3, and 9. All the effects of PGA-Cur were superior compared to the compounds used singly. PGA-Cur emerged as a useful dietary intervention for OA.

Druggable Prostanoid Pathway

Prostanoids (prostaglandins, prostacyclin and thromboxane) belong to the oxylipin family of biologically active lipids generated from arachidonic acid (AA). Protanoids control numerous physiological and pathological processes. Cyclooxygenase (COX) is a rate-limiting enzyme involved in the conversion of AA into prostanoids. There are two COX isozymes: the constitutive COX-1 and the inducible COX-2. COX-1 and COX-2 have similar structures, catalytic activities, and subcellular localizations but differ in patterns of expression and biological functions. Non-selective COX-1/2 or traditional, non-steroidal anti-inflammatory drugs (tNSAIDs) target both COX isoforms and are widely used to relieve pain, fever and inflammation. However, the use of NSAIDs is associated with various side effects, particularly in the gastrointestinal tract. NSAIDs selective for COX-2 inhibition (coxibs) were purposefully designed to spare gastrointestinal toxicity, but predisposed patients to increased cardiovascular risks. These health complications from NSAIDs prompted interest in the downstream effectors of the COX enzymes as novel drug targets. This chapter describes various safety issues with tNSAIDs and coxibs, and discusses the current development of novel classes of drugs targeting the prostanoid pathway, including nitrogen oxide- and hydrogen sulfide-releasing NSAIDs, inhibitors of prostanoid synthases, dual inhibitors, and prostanoid receptor agonists and antagonists.

A novel composite formulation of palmitoylethanolamide and quercetin decreases inflammation and relieves pain in inflammatory and osteoarthritic pain models

BACKGROUND

Osteoarthritis (OA) is a common progressive joint disease in dogs and cats. The goal of OA treatment is to reduce inflammation, minimize pain, and maintain joint function. Currently, non-steroidal anti-inflammatory drugs (e.g., meloxicam) are the cornerstone of treatment for OA pain, but side effects with long-term use pose important challenges to veterinary practitioners when dealing with OA pain. Palmitoylethanolamide (PEA) is a naturally-occurring fatty acid amide, locally produced on demand by tissues in response to stress. PEA endogenous levels change during inflammatory and painful conditions, including OA, i.e., they are typically increased during acute conditions and decreased in chronic inflammation. Systemic treatment with PEA has anti-inflammatory and pain-relieving effects in several disorders, yet data are lacking in OA. Here we tested a new composite, i.e., PEA co-ultramicronized with the natural antioxidant quercetin (PEA-Q), administered orally in two different rat models of inflammatory and OA pain, namely carrageenan paw oedema and sodium monoiodoacetate (MIA)-induced OA. Oral treatment with meloxicam was used as benchmark.

RESULTS

PEA-Q decreased inflammatory and hyperalgesic responses induced by carrageenan injection, as shown by: (i) paw oedema reduction, (ii) decreased severity in histological inflammatory score, (iii) reduced activity of myeloperoxidase, i.e., a marker of inflammatory cell infiltration, and (iv) decreased thermal hyperalgesia. Overall PEA-Q showed superior effects compared to meloxicam. In MIA-treated animals, PEA-Q exerted the following effects: (i) reduced mechanical allodynia and improved locomotor function, (ii) protected cartilage against MIA-induced histological damage, and (iii) counteracted the increased serum concentration of tumor necrosis factor alpha, interleukin 1 beta, metalloproteases 1, 3, 9 and nerve growth factor. The magnitude of these effects was comparable to, or even greater than, those of meloxicam.

CONCLUSION

The present findings shed new light on some of the inflammatory and nociceptive pathways and mediators targeted by PEA-Q and confirm its anti-inflammatory and pain-relieving effects in rodent OA pain models. The translatability of these observations to canine and feline OA pain is currently under investigation.