Apomorphine Effects on Pain in Parkinson's Disease

Apomorphine Effect on Pain in Parkinson's Disease: A Randomized, Double-blind Placebo Cross-over Study

To study the effects of acute apomorphine vs. placebo administration on different Parkinson's disease pain types.

Apomorphine is the only anti-parkinsonian agent compatible with levodopa in improving Parkinson's disease (PD) motor symptoms. Besides, it has positive effects on some of the nonmotor symptoms of the disease, such as urinary disturbances and sleep. Apomorphine is usually well tolerated as it produces limited side effects. Knowledge about the effects of apomorphine on pain in PD is scarce. Evidence on this topic has only been reported in case reports or small studies but represents a potentially important use of the drug. We hypothesize that apomorphine may be a rational, safe, and useful treatment for subjects with pain in PD, including different subtypes. Within this framework, the present study will evaluate the effect of acute apomorphine vs. placebo administration on different PD pain types.

Inclusion Criteria:

• Subjects with PD according to the MDS Clinical diagnostic criteria for Parkinson's disease.
• Participants on antiparkinsonian medication in advanced stages of the disease and experiencing OFF periods and pain.
• Apomorphine treatment naïve subjects or not received any within the last six months.
• Stable PD and pain medications for at least 30 days.
• Competence to self-report pain severity in the King's Parkinson's disease Pain Scale and a Likert Visual Analogue Scale.

Exclusion Criteria:

• Subjects who are unable to self-report pain severity in the selected scales. Patients that may require a translator or are illiterate will be included if they can self-report pain severity.
• Subjects with a diagnosis of dementia (Montreal Cognitive Assessment <20).
• Subject with poorly controlled orthostatic hypotension.
• Subjects associated with another medical condition, e.g., any cardiovascular, renal or hepatic impairment, hematological or psychiatric diseases.

Any contraindication to receiving apomorphine injections:

• Subjects who are hypersensitive to apomorphine or any ingredient in the formulation or component of the container (hydrochloric acid concentrated, sodium bisulfite (E222), and water)
• Subjects using concomitant drugs of the 5HT3 antagonist class including (e.g., ondansetron, granisetron, palonosetron)
• Subjects using concomitant antihypertensive medications or vasodilators
• Subjects with prolonged QT on an electrocardiogram.