Optimization and Evaluation of Trihexyphenidyl Hydrochloride Transdermal Patches Using Natural and Synthetic Polymers for Psychosis Management

Trihexyphenidyl hydrochloride (TPH) is an anticholinergic drug commonly used to manage psychosis-associated extrapyramidal symptoms and Parkinsonian disorders. However, its oral administration is associated with limitations such as first-pass metabolism, fluctuating plasma drug levels, and frequent dosing requirements, which may reduce patient compliance. The present study aimed to develop and optimize TPH-loaded transdermal patches using a combination of natural and synthetic polymers for sustained drug delivery. Patches were prepared by the solvent-casting method employing varying concentrations of hydroxypropyl methylcellulose (HPMC), chitosan, xanthan gum, and gum tragacanth. A factorial design was utilized to optimize formulation variables and evaluate their effects on physicochemical and drug-release characteristics. The prepared patches were assessed for thickness, weight variation, folding endurance, moisture content, moisture uptake, tensile strength, surface pH, drug content uniformity, and in vitro drug release. The optimized formulation exhibited satisfactory physicochemical properties, uniform drug distribution, good mechanical strength, and excellent flexibility. In vitro studies demonstrated sustained and controlled drug release over an extended period. The combination of natural and synthetic polymers significantly influenced the mechanical properties and release behavior, resulting in an optimized matrix system with improved performance. The developed transdermal patch represents a promising alternative to conventional oral therapy by providing sustained drug delivery, potentially enhancing therapeutic efficacy, patient compliance, and overall quality of life in long-term psychopharmacological management.