Pharmaceutical grade Naproxen possesses a logP value of around 3.3 and maintains preferential solubility in lipids. In a neutral pH environment Naproxen is mildly soluble in water; however, Naproxen-PEG conjugate indicates a lower logP value in that it demonstrates an increase in water solubility. Naproxen-PEG conjugate expresses an increase in hydrophilic preferences.