Parkinson’s disease (PD) is considered a neurodegenerative disorder of the nigrostriatal system. It is characterized by progressive motor dysfunction and treatment-related complications. Levodopa combined with carbidopa remains the cornerstone of therapy. Extended-release formulations may improve treatment stability and adherence. Objective: This study was conducted to compare immediate-release (IR) and extended-release (ER) carbidopa-levodopa formulations with respect to pharmacokinetics, clinical outcomes, and treatment adherence. Methodology: This observational study included 120 patients with idiopathic PD (65-75 years), who were assigned to two groups (n=60 each) receiving IR or ER formulations. Dose-normalized pharmacokinetic parameters (AUCτ/Dose, Cmax/Dose, Cavg/Dose, and Tmax) were analyzed. Clinical outcomes, including motor fluctuations, dyskinesia, and adherence, were examined over a 6-month follow-up period. Statistical comparisons were performed between the two groups. Key Findings: The IR formulation showed a higher Cmax/Dose (1.2 vs. 0.85, p < 0.001) and a shorter Tmax (1.0 vs. 2.5 h, p < 0.001), indicating a faster absorption profile. The ER formulation showed a slightly higher AUCτ/Dose (3.2 vs. 3.0, p = 0.28) and a lower Cavg/Dose (0.4 vs. 0.5, p = 0.01), reflecting a more sustained plasma profile. No statistically significant differences were found in motor fluctuations (17% vs. 12%) or dyskinesia (20% vs. 13%). However, treatment adherence was higher in the ER group. Conclusions: Although IR and ER formulations demonstrated similar clinical outcomes, the ER formulation was associated with a more stable pharmacokinetic profile and improved patient adherence. Recommendations: ER carbidopa-levodopa may be considered when simplified dosing and improved adherence are desired. Larger, long-term studies are needed to confirm its clinical advantages.

Parkinson’s disease (PD) is considered a neurodegenerative disorder of the nigrostriatal system. It is characterized by progressive motor dysfunction and treatment-related complications. Levodopa combined with carbidopa remains the cornerstone of therapy. Extended-release formulations may improve treatment stability and adherence. Objective: This study was conducted to compare immediate-release (IR) and extended-release (ER) carbidopa-levodopa formulations with respect to pharmacokinetics, clinical outcomes, and treatment adherence. Methodology: This observational study included 120 patients with idiopathic PD (65-75 years), who were assigned to two groups (n=60 each) receiving IR or ER formulations. Dose-normalized pharmacokinetic parameters (AUCτ/Dose, Cmax/Dose, Cavg/Dose, and Tmax) were analyzed. Clinical outcomes, including motor fluctuations, dyskinesia, and adherence, were examined over a 6-month follow-up period. Statistical comparisons were performed between the two groups. Key Findings: The IR formulation showed a higher Cmax/Dose (1.2 vs. 0.85, p < 0.001) and a shorter Tmax (1.0 vs. 2.5 h, p < 0.001), indicating a faster absorption profile. The ER formulation showed a slightly higher AUCτ/Dose (3.2 vs. 3.0, p = 0.28) and a lower Cavg/Dose (0.4 vs. 0.5, p = 0.01), reflecting a more sustained plasma profile. No statistically significant differences were found in motor fluctuations (17% vs. 12%) or dyskinesia (20% vs. 13%). However, treatment adherence was higher in the ER group. Conclusions: Although IR and ER formulations demonstrated similar clinical outcomes, the ER formulation was associated with a more stable pharmacokinetic profile and improved patient adherence. Recommendations: ER carbidopa-levodopa may be considered when simplified dosing and improved adherence are desired. Larger, long-term studies are needed to confirm its clinical advantages.