To provide a depot formulation for which depot formation is easy, and is capable of maintaining the depot form for a long period as desired, and in the case of containing a drug, to provide a depot formulation that sustained-releases the drug over a long period after being administered into the body. The present invention relates to a depot formulation containing a trialkyl citrate and/or an acetyl trialkyl citrate, in which the alkyl groups possessed by each of the trialkyl citrate and the acetyl trialkyl citrate are the same or different, and have a carbon number of 3 to 5.
