Characterization of a diltiazem-lambda carrageenan complex

Area of Science:

• Pharmaceutical Sciences
• Polymer Chemistry

Background:

• Diltiazem HCl is a calcium channel blocker used in treating cardiovascular conditions.
• Lambda carrageenan is a natural sulfated polysaccharide with potential applications in drug delivery.

Purpose of the Study:

• To investigate the interaction between lambda carrageenan and diltiazem HCl.
• To quantify the binding capacity of lambda carrageenan for diltiazem.
• To assess the impact of this interaction on diltiazem release from hydrophilic matrix systems.

Main Methods:

• Dialysis equilibria were employed to determine binding capacity.
• Matrix tablets with varying lambda carrageenan concentrations were prepared.
• Drug release profiles were analyzed.
• X-ray and Differential Scanning Calorimetry (DSC) were used for solid-state characterization.

Main Results:

• A significant interaction and binding capacity between lambda carrageenan and diltiazem HCl were observed.
• The binding capacity was found to be largely insensitive to pH (1.8-6.8) but decreased with increasing ionic strength, indicating ionic bond involvement.
• Drug release from matrix tablets correlated with lambda carrageenan content, demonstrating the interaction's relevance to drug delivery.
• Solid-state analysis provided preliminary characterization of the diltiazem-carrageenan complex.

Conclusions:

• Lambda carrageenan effectively binds diltiazem HCl, influencing its release kinetics in hydrophilic matrices.
• The diltiazem-carrageenan interaction is primarily governed by ionic forces and is robust across a relevant pH range.
• Understanding this interaction is vital for optimizing diltiazem HCl formulations using lambda carrageenan as a matrix former.