Cardiovascular and electrocardiographic effects of the dopamine receptor agonists ropinirole, apomorphine, and PNU-142774E in conscious beagle dogs

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

OBJECTIVE

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

DESIGN

Prospective, crossover study design.

SETTING

Institutional animal research facility.

ANIMALS

Six healthy male purpose-bred Beagle dogs.

INTERVENTIONS

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.

MEASUREMENTS AND MAIN RESULTS

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.

CONCLUSIONS

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.

Ropinirole eye drops induce vomiting effectively in dogs: a randomised, double-blind, placebo-controlled clinical study

There is a need for an effective and safe emetic agent that dog owners could easily administer to their dogs following veterinary advice in cases of potential poisoning. As a response to this need, a randomised, double-blind, multi-site, clinical field study was performed to assess the efficacy, safety and usability of ropinirole eye drops to induce vomiting in dogs. Ropinirole (target dose 3.75 mg/m²) was applied to eyes of 100 dogs, and 32 dogs received placebo. The drug was administered by the dog owner at a veterinary clinic under the supervision of a veterinarian and led to vomition in 95% of the ropinirole-treated dogs within 30 min. The median time to first vomit was 10 min (range: 3–37 min). None of the dogs receiving placebo vomited in this time period. All owners were able to administer the product and 96% of them assessed the administration to be very easy or easy, which was confirmed by the observing veterinarian. Some ocular signs were seen both with ropinirole and placebo, hyperaemia being the most common. All observed signs were transient and in most cases mild. Ropinirole eye drops provided an effective, safe and reliable means to induce emesis in dogs.

Ventricular bigeminy after subcutaneous administration of apomorphine in a patient with refractory Parkinson's disease: a case report

Apomorphine is a well established treatment for the management of sudden, unexpected and refractory levodopa-induced “off” states in fluctuating Parkinson’s disease either as bolus injections or as continuous infusions. Incidents of atrial fibrillation associated with the administration of the drug have been reported in the past but no incidents of ventricular arrhythmias. We report a case of ventricular bigeminy recorded in a female patient after the administration of apomorphine.

Effects of ropinirole on action potential characteristics and the underlying ion currents in canine ventricular myocytes

In spite of its widespread clinical application, there is little information on the cellular cardiac effects of the dopamine receptor agonist ropinirole. In the present study, therefore, the concentration-dependent effects of ropinirole on action potential morphology and the underlying ion currents were studied in enzymatically dispersed canine ventricular cardiomyocytes using standard microelectrode, conventional whole-cell patch clamp, and action potential voltage clamp techniques. At concentrations > or = 1 microM, ropinirole increased action potential duration (APD(90)) and suppressed the rapid delayed rectifier K(+) current (I (Kr)) with an IC(50) value of 2.7 +/- 0.25 microM and Hill coefficient of 0.92 +/- 0.09. The block increased with increasing depolarizations to more positive voltages, but paradoxically, the activation of I (Kr) was accelerated by 3 muM ropinirole (time constant decreased from 34 +/- 4 to 14 +/- 1 ms). No significant changes in the fast and slow deactivation time constants were observed with ropinirole. At higher concentrations, ropinirole decreased the amplitude of early repolarization (at concentrations > or = 10 microM), reduced the maximum rate of depolarization and caused depression of the plateau (at concentrations > or = 30 microM), and shortened APD measured at 50% repolarization (at 300 microM) indicating a concentration-dependent inhibition of I (to), I (Na), and I (Ca). Suppression of I (Kr), I (to), and I (Ca) has been confirmed under conventional patch clamp and action potential voltage clamp conditions. I (Ks) and I (K1) were not influenced significantly by ropinirole at concentrations less than 300 microM. All these effects of ropinirole were fully reversible upon washout. The results indicate that ropinirole treatment may carry proarrhythmic risk for patients with inherited or acquired long QT syndrome due to inhibition of I (Kr)-especially in cases of accidental overdose or intoxication.