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OBJECTIVE The aim of this study was to determine whether the pharmacokinetics of maropitant, administered SC as a commercially available maropitant-containing injectable product (Cerenia Injectable), differ when combined with lactated Ringer solution prior to administration. ANIMALS We used 6 adult spayed female Beagle dogs between 3 and 6 years of age, with a mean weight of 9.58 kg. PROCEDURES In this randomized crossover study, the dogs underwent 2 treatment protocols separated by a 14-day washout period: (1) an SC injection of 1 mg/kg of Cerenia Injectable (maropitant citrate; 10 mg/mL) and (2) 1 mg/kg of Cerenia Injectable diluted in 10 mL/kg of lactated Ringer injectable solution (LRS) given SC. Plasma maropitant concentrations were assessed by mass spectrometry. Pharmacokinetic analysis was performed using pharmacokinetic and pharmacodynamic data-analysis software to determine maximum plasma concentration (Cmax), time to reach maximum concentration, half-life, total exposure to the drug, mean residence time, clearance rate per fraction absorbed, and absorption and elimination kinetic parameters. RESULTS Cmax was reduced by 26% (P = .002), the absorption rate constant decreased 80% (P = .031), and the absorption half-life increased when Cerenia was administered diluted in LRS. CLINICAL RELEVANCE Administration of maropitant (Cerenia) diluted in LRS had a pharmacokinetic impact, resulting in a significantly reduced Cmax and slower absorption. Clinical efficacy was not assessed in this study.