Synthesis of a new mPEG-dexamethasone conjugate and preliminary bioavailability studies in rabbits

Poly(ethylene glycol) esters have been proposed as a potential oral-controlled drug delivery system for dexamethasone (DXM). The drug was covalently attached to monomethoxypolyethylene glycol canine (mPEG-NH2) (Mw = 10,000 Da) using a succinate linker. A new PEG-based prodrug system was designed using ester derivatives. The drug-polymer conjugate (mPEG-DXM) was freely water soluble at room temperature. First of all, the adduct hydrolytic stability was assessed at physiological pH. Then, the bioavailability was evaluated by orally administering the mPEG-DXM conjugate in rabbits and comparing to that obtained by the intravenous route. The area tinder the concentration-time curve (AUC) of PEGylated drug was twice as large as that of the parent drug after oral administration. In conclusion, PEGylated DXM was useful for maintaining the DXM concentration in the blood after oral administration.