Effect of nonionic surfactants on aqueous primidone suspensions

Area of Science:

• Pharmaceutical Sciences
• Physical Chemistry
• Colloid Science

Background:

• Primidone is a sparingly soluble drug used in pharmaceutical formulations.
• Surfactants like octoxynol 9 are often employed to enhance drug solubility and stability in suspensions.
• Understanding surfactant-drug interactions is crucial for optimizing drug delivery systems.

Purpose of the Study:

• To investigate the interactions between octoxynol 9 and primidone in aqueous suspension.
• To quantify the effects of octoxynol 9 on primidone adsorption, micellar solubilization, and particle deflocculation.
• To evaluate the influence of varying octoxynol concentrations and structures on primidone suspension properties.

Main Methods:

• Adsorption/desorption isotherms of octoxynol 9 on primidone particles.
• Measurement of primidone's micellar solubilization in the presence of octoxynol 9.
• Determination of suspension sedimentation volume as a measure of deflocculation.
• Comparative studies using different octoxynols with varying hydrophilic-lipophilic balance (HLB).

Main Results:

• Octoxynol 9 adsorption on primidone reached saturation, forming a monolayer, and was largely reversible.
• Micellar solubilization of primidone by octoxynol 9 was limited.
• Sedimentation volume of primidone suspensions decreased with increasing octoxynol 9 concentration, stabilizing near the critical micelle concentration (0.018%).
• Agitation prior to sedimentation induced flocculation within a specific concentration range.
• Octoxynols with higher HLB values showed reduced surface activity and adsorption, leading to larger sedimentation volumes.

Conclusions:

• Octoxynol 9 exhibits reversible adsorption on primidone, with saturation occurring at higher concentrations.
• While micellar solubilization is minimal, octoxynol 9 effectively deflocculates primidone particles, reducing sedimentation volume.
• The deflocculation efficiency is concentration-dependent and influenced by the surfactant's HLB, with higher HLB octoxynols being less effective due to lower adsorption.
• These findings provide insights into optimizing primidone suspension formulations using nonionic surfactants.