The invention provides opioid agonists, in particular morphine and codeine, covalently bound to a water-soluble oligomer, namely a polyethylene glycol (PEG) oligomer having reduced potential for substance abuse and uses thereof. The compounds of the invention possess altered pharmacokinetic profiles relative to the opioid agonists alone, but are not subject to the risk of physical tampering that allows for the recovery and abuse of the opioid agonist associated with certain alternative delivery formulations.
