Interpolymer Complexation Between Polyox and Carbopol, and Its Effect on Drug Release From Matrix Tablets

Area of Science:

• Pharmaceutical Sciences
• Polymer Chemistry
• Materials Science

Background:

• Polyethylene oxide (Polyox) and Carbopol 907 are commonly used polymers in drug delivery.
• Understanding their interaction is crucial for designing controlled-release formulations.
• pH-dependent interactions can significantly impact drug release kinetics.

Purpose of the Study:

• To investigate the pH-dependent interaction between Polyox N12K and Carbopol 907.
• To characterize the resulting interpolymer complex.
• To evaluate the effect of these interactions on theophylline release from tablet formulations.

Main Methods:

• Complexation studies in aqueous media at varying pH.
• Characterization of the interpolymer complex using glass transition temperature (Tg) measurements.
• Theophylline release studies from tablets containing both polymers in different dissolution media (HCl, acetate buffer, phosphate buffer).
• Analysis of drug release mechanisms (Fickian diffusion, gel erosion, anomalous transport).

Main Results:

• A hydrogen bond-induced complex formed between pH 5.0 and 6.0, precipitating at pH 4.0.
• The complex exhibited an amorphous nature with Tg of 3.17°C and a molar ratio of 1.3:1 (ethylene oxide:acrylic acid).
• Theophylline release was highly pH-dependent: Fickian diffusion in HCl (93% release in 27h), gel erosion at pH 4.0, and anomalous transport at pH 6.8.
• Sustained release over 12h was achieved at pH 4.0 and pH 6.8, with statistically similar release profiles.

Conclusions:

• The interaction between Polyox N12K and Carbopol 907 is strongly pH-dependent, leading to the formation of an interpolymer complex.
• This pH-dependent complexation effectively modulates theophylline release kinetics, allowing for controlled drug delivery.
• The study demonstrates the potential of combining Polyox and Carbopol for developing pH-responsive, sustained-release pharmaceutical formulations.