Ropinirole is a full dopamine agonist with high selectivity for the dopamine D2-like receptor family (D2, D3 and D4 receptors). It induces emesis by activating the D2-like receptors in the chemoreceptor trigger zone, located in the area postrema, which transmits the information to the emesis centre to trigger vomiting.

In a clinical field trial including 100 clinically healthy dogs treated with Clevor, the time from administration to first vomit was 3–37 minutes with a mean time of 12 minutes and median time of 10 minutes. The time between the first to the last vomit was 0–108 minutes (0 if the dog vomited only once) with a mean duration of 23 minutes and a median duration of 16 minutes. Within 30 minutes 95% of the dogs vomited. An additional dose was administered after 20 minutes to 13% of the dogs because of lack of efficacy. Three dogs (3%) did not vomit at all despite an additional dose. 5% of the dogs in the clinical study received anti-emetic treatment (metoclopramide) because their vomiting persisted for more than 60 minutes.

Ropinirole is rapidly absorbed into the systemic circulation of dogs after administration as a solution on their eye surface. At the target dose of 3.75 mg/m² (equivalent to 2–15 µl/kg bw), a peak plasma concentration (Cmax) of 26 ng/ml is reached 10 to 20 minutes (tmax) after administration. The systemic bioavailability of the drug by this ocular route of administration is 23%. Vomiting starts before the Cmax in plasma is reached; at 4–6 minutes in a pharmacokinetic study in dogs. No direct correlation between ropinirole concentration in plasma and the duration of vomiting was observed after ocular administration. The time to last vomit ranged from 30 to 82 minutes following ocular administration in a pharmacokinetic study in dogs.

Ropinirole is rapidly distributed and has a relatively high apparent volume of distribution. In dogs, the volume of distribution (Vz) is 5.6 l/kg after intravenous administration. The fraction bound to plasma proteins in dogs is low (37%).

Ropinirole is mainly eliminated by hepatic metabolism. The half-life of elimination (t½) is 4 hours after intravenous administration to dogs. Biotransformation occurs by dealkylation, hydroxylation and subsequent conjugation with glucuronic acid or oxidation to carboxylic acid. About 40% of radioactive ropinirole is excreted in the urine within 24 hours after intravenous administration to dogs. Excretion in the urine occurs mainly as metabolites. The portion recovered as unchanged ropinirole in the urine is below 3% within the first 24 hours.