To evaluate the efficacy and tolerability of subcutaneous foslevodopa/foscarbidopa infusion and to identify clinical predictors of discontinuation in patients with complicated Parkinson’s disease (PD).  

Levodopa is the most effective symptomatic therapy for PD; however, oral administration may be complicated by motor fluctuations. Foslevodopa/foscarbidopa, a soluble levodopa formulation delivered as continuous subcutaneous infusion, aims to maintain stable plasma drug concentrations. However, patient characteristics predicting a favorable response remain unclear.

Patients diagnosed with PD and initiated on subcutaneous foslevodopa/foscarbidopa infusion were retrospectively identified using an institutional electronic data explorer. Oral-to-subcutaneous dose conversion was calculated using the following formula: infusion rate (mL/hr) = [(total daily levodopa dose × 1.3) ÷ 240] ÷ total daily hours awake.

A total of 23 patients were included; 18 had early-onset PD. The average disease duration was 7 years. A family history of movement disorders was present in 39%, and 10 of 17 who underwent genetic testing carried a PD-related mutation. Prior to infusion initiation, all patients exhibited severe motor fluctuations, and more than half experienced treatment-induced dyskinesias (57.7%) or dystonia (53.9%). In total, 13 patients (56.5%) reported a robust response to infusion compared with oral therapy, whereas 10 (43.5%) discontinued treatment due to poor symptom control (n=5), behavioral dyscontrol (n=3), or infusion-site reactions (n=2). Compared with responders, those who discontinued treatment had higher rates of orthostatic hypotension (30% vs. 15%), anxiety (90% vs. 54%), REM-sleep behavior disorder (20% vs. 0%), as well as higher prevalence of positive genetic testing (80% vs. 50%).

Subcutaneous foslevodopa/foscarbidopa is a promising therapeutic option that effectively reduces motor fluctuations and improves symptom control in complicated PD. However, its use may be limited by adverse effects, particularly among patients with baseline behavioral changes, autonomic features, and sleep disorders. Individualized patient evaluation and close monitoring are essential to optimize benefits and minimize discontinuation.