Development of an in-situ forming implant system for levodopa and carbidopa for the treatment of parkinson’s disease

Long-acting injectables have gained attraction as a system for treating chronic conditions due to their increased efficacy, safety, and patient compliance. Currently, patients with Parkinsons need to administer oral medications multiple times a day which imposes the significant risk of non-compliance. This study aimed to design an in-situ implant-forming system for controlled delivery of levodopa and carbidopa for up to 1 week which will reduce the need for multiple dosing. The combination of poly-lactic-co-glycolic acid (PLGA _50:50) and Eudragit L-100 was used to prepare the implants and the formulation was optimized to achieve a controlled release over 7 days. The optimized formulation containing 26% PLGA and 6% Eudragit L 100 displayed a favorable release profile and injectability with low viscosity. The optimized formulation in vitro release study revealed an initial burst of 34.17% and 37.16% for levodopa and carbidopa in the first 24 h and about 92% and 81% release within 7 days. A good correlation was observed between the in-vitro drug release data and ex-vivo drug release with a correlation coefficient of 0.91 for levodopa and 0.90 for carbidopa. Viscosity analysis showed the Newtonian behavior of the formulation. Syringeability analysis of the formulation showed that the maximum force required for expelling the formulation was 32.98 ± 0.72 N using a 22 G needle. The in-vitro degradation studies revealed 81.89% weight loss of implant in 7 days. The prepared formulation was assessed for in-vivo performance using a convolution modeling technique using a convolve function in R software. The predicted AUC 0-∞ h for the in-situ forming implant was 26505.5 ng/ml with Cmax, 399.3 ng/ml, and Tmax 24 h assuming 100% bioavailability. The results justify that the prepared in-situ implant forming system can be a promising system for the delivery of levodopa and carbidopa for Parkinson's patients.