New Parkinson’s Therapies: Subcutaneous Infusion Options Expand Treatment Landscape

For individuals living with Parkinson’s disease (PD) experiencing motor fluctuations, new treatment options are emerging beyond traditional oral medications. Subcutaneous (SC) infusion therapies, delivering medication directly under the skin, are gaining traction as a viable alternative to surgical interventions. This article explores the current landscape of SC infusion therapies, their clinical evidence, and practical considerations for implementation, drawing on recent approvals and expert insights.

Understanding Parkinson’s Disease and Motor Fluctuations

Parkinson’s disease is the second most common neurodegenerative disorder, characterized by bradykinesia (slowness of movement) plus either rest tremor or rigidity.¹ While levodopa remains a cornerstone of treatment, long-term use often leads to motor fluctuations – unpredictable “on” and “off” periods where symptoms are either well-controlled or poorly controlled.² These fluctuations can significantly impact quality of life.

The Rise of Subcutaneous Infusion Therapies

Traditionally, managing advanced PD with motor fluctuations involved adjusting oral medications, adding adjunctive therapies, or considering surgical options like deep brain stimulation (DBS) or jejunostomy tube placement. However, recent advancements have introduced SC infusion therapies as a less invasive alternative. These therapies bypass the gastrointestinal tract, providing continuous dopaminergic stimulation and avoiding the peaks and troughs associated with oral medication.³

Approved SC Infusion Therapies

As of March 2026, two primary SC infusion therapies are approved for the treatment of Parkinson’s disease:

Onapgo (Apomorphine)

Approved by the FDA in February 2025, Onapgo delivers a continuous infusion of apomorphine, a dopamine agonist, to control motor symptoms like tremor.^4,5 The TOLEDO study demonstrated that Onapgo reduced signify “off” time by almost 2 hours per day compared to placebo.⁶ Improvements were sustained over 52 weeks, with increased “on” time and reduced oral levodopa dosage.⁶ Common side effects include infusion site reactions, nausea, and somnolence.⁶

Foscarbidopa/Foslevodopa

Foscarbidopa and foslevodopa are prodrugs of carbidopa and levodopa, respectively. Clinical trials have shown that foscarbidopa/foslevodopa increases “on” time without troublesome dyskinesia and reduces “off” time.^7,8 However, infusion site reactions, including erythema, pain, and cellulitis, are common.^7,8

When to Consider SC Infusion Therapy

Experts suggest considering SC infusion for patients who meet certain criteria, often summarized by the “5-2-1” rule: requiring levodopa dosing ≥5 times daily, experiencing ≥2 hours per day with “off” symptoms, or having ≥1 hour per day of troublesome dyskinesia.⁹ SC infusion can be a good option for patients who haven’t achieved adequate symptom control with oral medications or experience significant motor fluctuations.¹⁰ It can also serve as a “bridging therapy” before considering DBS.¹¹

Choosing Between Apomorphine and Foscarbidopa/Foslevodopa

The choice between Onapgo and foscarbidopa/foslevodopa depends on individual patient factors. Factors to consider include prior response to oral levodopa or dopamine agonists, predisposition to side effects, and symptom profile.¹² Switching between therapies is relatively easy, allowing clinicians to tailor treatment based on patient response.¹²

Practical Considerations for SC Infusion

• Education and Training: Thorough patient and caregiver education on infusion set management, hygiene, and troubleshooting is crucial.
• Infusion Site Management: Frequent infusion set changes (daily is often recommended) and systematic site rotation are essential to minimize skin reactions.¹³
• Titration: Initiation and titration should be closely monitored, either in a hospital setting or with frequent outpatient follow-up.
• Adverse Event Management: Be prepared to manage infusion site reactions and other potential side effects, such as nausea or hallucinations.

Future Directions

Ongoing research, such as the ROSSINI study evaluating long-term safety and tolerability of foscarbidopa/foslevodopa, will continue to refine our understanding of SC infusion therapies.¹⁴ Advances in infusion set technology and a growing body of clinical experience are expected to further optimize treatment outcomes and improve the quality of life for individuals with Parkinson’s disease.

Disclaimer: This article provides general information and should not be considered medical advice. Always consult with a qualified healthcare professional for diagnosis and treatment of Parkinson’s disease.