An experimental study of consecutive administration of ropinirole and apomorphine for emesis induction in dogs

To study the safety and effectiveness of consecutively administered ropinirole and apomorphine (both dopamine 2-like receptor agonists) for emesis induction in dogs.

Prospective, crossover study design.

Institutional animal research facility.

Six healthy male purpose-bred Beagle dogs.

Each dog received 4 treatments: (1) apomorphine infusion (21 μg/kg) over 30 minutes + ropinirole eye drops (3.75 mg/m² ); (2) ropinirole infusion (108 μg/m² ) over 30 minutes + apomorphine SC (100 μg/kg); (3) apomorphine SC (100 μg/kg) + ropinirole eye drops (7.5 mg/m² ) after 30 minutes; and (4) ropinirole eye drops (7.5 mg/m² ) + apomorphine SC (100 μg/kg) after 30 minutes. Infusions were administered via a catheter instrumented in the cephalic vein. Eye drops and SC injections were administered as described in the product inserts. Blood samples were taken for ropinirole and apomorphine concentration analysis before dosing and periodically following administrations. The washout period between the treatments was 5-7 days.

Number of vomits and clinical signs were recorded. Alertness and heart rate were monitored in conjunction with blood sampling. The average number of vomits varied between 4.3 and 8.8 (range 1-16) following treatments. Signs of nausea, vomiting, and lethargy were seen in all individuals without significant differences between treatments. Moderate to marked, transient increase in heart rates was detected in all treatments. Infrequent noted side effects included ocular hyperemia, blepharospasms, and muscle tremors. Prior treatment with apomorphine significantly decreased the absorption of ropinirole eye drops.

The safety and efficacy profiles of this experimental study support that ropinirole and apomorphine could be administered consecutively in cases where the treatment using 1 substance has resulted in an incomplete evacuation of the stomach contents, and the attending veterinarian considers the use of a different agent to have benefits that outweigh the risks.