A method is provided for preparing drug formulations suitable for electrotransport drug delivery. The drug to be delivered, present in salt form, is contacted with an ion exchange material prior to incorporation into the reservoir (26) of an electrotransport delivery system (10). In this way, the drug salt is partially or completely neutralized. This technique is useful for adjusting the pH of the drug formulation without incorporating extraneous materials, e.g., competing ions or the like, into the reservoir (26).