The present disclosure relates to methods for making extended-release formulations of water-soluble active pharmaceutical ingredients such as metformin HCl. In one aspect, the disclosure provides a method that includes adding an aqueous solution of an active pharmaceutical ingredient to an agitated mixture of one or more release-modifying polymers and optionally one or more binders in one or more organic solvents, the one or more organic solvents together being an antisolvent for the active pharmaceutical ingredient, water being sufficiently soluble in the one or more organic solvents such that the water added as part of the aqueous solution dissolves in the mixture, the addition thereby precipitating the active pharmaceutical ingredient; separating the active pharmaceutical ingredient and the one or more release-modifying polymers and, if present, the one or more binders from the one or more organic solvents to yield co-processed particles; and drying the co-processed particles. The methods can be used to make dosage forms such as tablets having reduced amounts of release-modifying polymers.