Provided is an extended release formulation which is capable of controlling dissolution of a drug and of enduring peristaltic movement of the gastrointestinal tract. Specifically, the present invention is: a solid formulation comprising a drug, croscarmellose sodium, alkali metal salt or alkoxide, and an alkali agent, the alkali metal salt being a sodium salt or potassium salt, and the alkali agent being a magnesium oxide or a solid formulation comprising a drug, croscarmellose sodium, alkali metal salt or alkoxide, and a water-soluble polymer or hydrophobic base, the alkali metal salt being a sodium salt or potassium salt. The present invention is thus capable of providing an extended release formulation that controls dissolution of a drug and endures peristaltic movement of the gastrointestinal tract.
