[Examination of the cause of changing solution color by mixing aminophylline and dopamine, the compatibility of which was indicated by the supplier].

A case in which aminophylline solution was administered to a patient with congestive heart failure is reported and the problems caused by administration were solved by subsequent experiments. Dopamine solution was added from the side route using a mechanical pump, and mixed with aminophylline solution in the main route. Furosemide was administered after clamping and flushing the main route according to the supplier's information that indicated the compatibility of dopamine and aminophylline. However, the aminophylline solution turned black in color 3 h after furosemide administration. Several examinations were carried out to clarify the cause of the incompatibility in this case. The results showed that solutions with all possible combinations, including aminophylline and dopamine, turned black at 24 h after mixing, and the UV absorption at 430 nm increased from 0 to 0.28. UV absorption of the mixed solution increased in a dopamine dose-dependent manner in the range of 1.5-12 mg. When aminophylline was added to physiological saline or hypotonic electrolyte solution, the pH of each solution increased. These results suggested that degradation of dopamine to a melanin-like polymer under alkaline conditions caused the change in color of the solution. It is presumed that dopamine was inappropriately injected into aminophylline solution as the route was clamped tightly to shut out furosemide contamination. Aminophylline and dopamine are often co-administered to patients in critical condition. Thus, even if compatibility of aminophylline with dopamine is indicated by the supplier, they should be administered through separate routes.