Abstract
Background: The drug release of antiparkinsonian drugs is an important issue during the formulation process because proper release kinetics can help to reduce the off periods of Parkinson’s disease. A 2-factor, 3-level (32) full-factorial design was conducted to evaluate statistically the influence of the hydrophobicity of mesoporous silica on drug release. Methods: Hydrophobization was evaluated by different methods, such as contact angle measurement, infrared spectroscopy and charge titration. After loading the drug (levodopa methyl ester hydrochloride, melevodopa hydrochloride, LDME) into the mesopores, drug content, particle size, specific surface area and homogeneity of the products were also analyzed. The amorphous state of LDME was verified by X-ray diffractometry and differential scanning calorimetry. Results: Drug release was characterized by a model-independent method using the so-called initial release rate parameter, as detailed in the article. The adaptability of this method was verified; the model fitted closely to the actual release results according to the similarity factor, independently of the release kinetics. Conclusions: The API was successfully loaded into the silica, resulting in a reduced surface area. The release studies indicated that the release rate significantly decreased (p < 0.05) with increasing hydrophobicity. The products with controlled release can reduce the off period frequency.
Highlights
Several active pharmaceutical ingredients (APIs) have a narrow therapeutic index, such as levodopa (LD)
mesoporous silicas (MPSs) was hydrophobized by TMCS; the model API was LDME
The wettability of MPSs was reduced by using TMCS; the silanol group density decreased, and the trimethylsilyl groups were attached to the surface
Summary
Several active pharmaceutical ingredients (APIs) have a narrow therapeutic index, such as levodopa (LD). As the traditional—orally administered—LD therapy progresses, the therapeutic window (on time) becomes narrow, and the blood level becomes unpredictable [4]. This leads to side effects, called LD-related motor complications (LRMCs) [5,6], resulting in the so-called on-off phenomenon [7,8], which could be managed by the efficient control of drug release. Results: Drug release was characterized by a model-independent method using the so-called initial release rate parameter, as detailed in the article The adaptability of this method was verified; the model fitted closely to the actual release results according to the similarity factor, independently of the release kinetics.
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