A concomitant agent to be used simultaneously or separately, comprising a combination of (a) 3-{(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl}thiazolidine, a salt of the compound with an organic or inorganic and mono- or di-basic acid or a solvate thereof, and (b) at least one kind of active ingredient selected from the group consisting of an active ingredient of a pharmaceutical agent selected from (i) an antidiabetic drug, (ii) a lipid lowering drug, (iii) an antihypertensive drug, (iv) a therapeutic drug for diabetic complications, (v) an antiobesity drug, (vi) an antiplatelet drug and (vii) an anticoagulant, a pharmaceutically acceptable salt thereof and a solvate thereof.
