2014 年 40 巻 4 号 p. 252-257
For patients experiencing dysphagia, especially those who have undergone neurosurgery and have been prescribed multiple medications, the simple suspension method is a useful way of simultaneously administering multiple drugs. However, little is known about the incompatibility of drugs administered simultaneously according to this method. In the present study, we assessed the amount of active pharmaceutical ingredients remaining in the suspension on suspending sodium valproate, warfarin potassium, amlodipine besylate, and magnesium oxide simultaneously. When the Norvasc®OD tablet was suspended with Magmitt® tablet, the recovery amount of amlodipine remaining in the suspension decreased significantly in an exposure time-dependent manner. The decrease in amlodipine was also observed when the Norvasc®OD tablet or amlodipine besylate was suspended in a basic buffer (pH 10). Furthermore, the decrease was accompanied by degradation of amlodipine. These results suggest that the degradation of amlodipine caused by the increase in pH led to the decrease in amlodipine. In conclusion, the results of this study suggest that it is necessary to pay attention to simultaneous suspension of amlodipine and drugs that increase the pH of the suspension.