Modulation of aggregation behavior of amphiphilic drug AMT under the influence of polymer molecular weight and composition

The purpose of this study was to determine the aggregation behavior of amphiphilic drug amitriptyline hydrochloride (AMT) and to search for means which boost/suppress the aggregation behavior. Polyethylene glycols (PEGs) nonionic polymers (which are used as pharmaceutical excipients) of varying molecular weights from 400 to 35,000 were tested. To know their effect on the micellization and interfacial behavior of the drug, the critical micelle concentration (CMC) and critical aggregation concentration (CAC) were determined in presence of various polymers by tensiometric and conductivity methods. The CAC values were found to decrease while the CMC values increased with increase in the polymer concentration. The thermodynamic parameters were evaluated where ΔG°mic and ΔG°agg are found to be negative, confirming the feasibility of interaction between AMT and polymers.

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► Polymer–drug complex microstructures depend on the composition and chain length of the polymer.
► The CMC values of AMT (amphiphilic drug) increase as the concentration and (PEG) polymer molecular weight increase.
► The CAC values decrease with increase in concentration and polymer molecular weight.