The invention relates to a composition comprising a suspension which comprises an admixture of a hydrophobic medium and a solid form wherein the solid form comprises a therapeutically effective amount of a therapeutic agent and at least one salt of a medium chain fatty acid, and wherein the medium chain fatty acid salt is present in the composition at an amount of 10% or more by weight, wherein the therapeutic agent is a polypeptide. The invention also relates to compositions for use in treating or preventing diseases by administration of the compositions to affected subjects.