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Pharmacological particulars
Pharmacotherapeutic group: Other anti-inflammatory and antirheumatic agents, non-steroids
ATCvet code: QM01AX92
Pharmacodynamic properties
Grapiprant is a non-steroidal, non-cyclooxygenase inhibiting anti-inflammatory drug in the piprant class. Grapiprant is a selective antagonist of the EP4 receptor, a key prostaglandin E2 receptor that predominantly mediates prostaglandin E2‐elicited nociception. The specific effects of the binding of prostaglandin E2 to the EP4 receptor include vasodilation, increased vascular permeability, angiogenesis and production of pro‐inflammatory mediators. The EP4 receptor is important in mediating pain and inflammation as it is the primary mediator of the prostaglandin E2-elicited sensitization of sensory neurons and prostaglandin E2-elicited inflammation.
Pharmacokinetic particulars
Grapiprant is readily and rapidly absorbed from the gastrointestinal tract in dogs. After a single oral dose of 2 mg grapiprant/kg, Cmax and AUC values of 1.21 μg/ml and 2.71 μg.h/ml were reached in the fasted state. Maximum grapiprant concentrations are observed in serum within one hour of dosing in the fasted state. Intake of the tablet with food reduces the oral bioavailability, i.e. the oral bioavailability of grapiprant when taken in the fasted state was 89% and when taken with food it was 33%, with mean Cmax and AUC grapiprant values reduced 4-fold and 2-fold, respectively. Grapiprant does not accumulate in the dog after repeated administration. No gender related differences in absorption are observed.
In vitro protein binding of grapiprant indicates that grapiprant is primarily bound to dog serum albumin. The mean percentage of unbound grapiprant was 4.35% and 5.01% at a grapiprant concentration of 200 ng/ml and 1000 ng/ml.
Grapiprant is primarily bound to serum proteins. In dogs, grapiprant is a major excretion product in bile, faeces and urine. Four metabolites are identified and the metabolic pathways include N-deamination to form the major metabolite in faeces (7.2%) and urine (3.4%). Two hydroxylated metabolites and one N-oxidated metabolite are also recovered in bile, faeces and/or urine. The pharmacological activity of the metabolites is not known.
Grapiprant is primarily excreted via faeces. Approximately 70-80% of the administered dose is excreted within 48-72 h with the majority of the dose excreted unchanged. Faecal excretion accounted for roughly 65% of the dose whereas approximately 20% of the dose was excreted through urine.
The elimination half-life of grapiprant is approximately 4.6 to 5.67 hours.