The stability of both drug components of admixtures of milrinone and epinephrine, atropine sulfate, lidocaine hydrochloride, morphine sulfate, calcium chloride, or sodium bicarbonate injections was studied. Duplicate solutions of admixtures of milrinone injection 1 mg/mL and epinephrine injection 1:10,000, atropine sulfate injection 1 mg/mL, lidocaine hydrochloride injection 1%, morphine sulfate injection 8 mg/mL, calcium chloride injection 10%, or sodium bicarbonate injection 7.5% were prepared and stored in glass containers at 22-23 degrees C under fluorescent light. Samples were taken immediately and after 20 minutes for assay by high-performance liquid chromatography (HPLC). Milrinone at initial concentrations of 0.10-0.73 mg/mL showed no degradation in any of the solutions during the study period, nor was any degradation observed for lidocaine, morphine, atropine, or epinephrine. Milrinone 0.10-0.73 mg/mL is compatible with atropine sulfate, lidocaine hydrochloride, epinephrine, calcium chloride, or sodium bicarbonate in glass containers stored for 20 minutes at room temperature. These results support the use of milrinone in combination with these agents immediately after the preparation of admixtures.