Establishing Evidence on Important Patient Characteristics and Indications for Use of Non-Prescription Drugs Containing Magnesium Oxide

Magnesium oxide is contained in various non-prescription drugs; specifically, it is the main component of laxatives and is contained in absorption enhancers used for antipyretic analgesics. Important safety information is being collected as the use of magnesium oxide formulations has been associated with the risk of hypermagnesemia and mortality. In order to prevent severe adverse effects associated with hypermagnesemia following the use of non-prescription drugs that contain magnesium oxide, we aimed to establish evidence on important patient characteristics and indication for use of magnesium oxide formulations to help inform pharmacists and registered sellers. We examined the package inserts and identified that the maximum daily dose of magnesium oxide contained in laxatives and over-the-counter (OTC) drugs was approximately 2,000 mg, which is equivalent to the dose contained in prescription drugs. Furthermore, none of the drugs indicated specific dose considerations for kidney function in the package insert for patients. Analysis of the Japanese Adverse Drug Event Report (JADER) further demonstrated that the risk of mortality following the onset of hypermagnesemia was approximately twice as high in individuals over the age of 60 years. Additional meta-analysis demonstrated that the use of magnesium oxide was associated with elevated risk of hypermagnesemia in patients with kidney dysfunction (≥chronic kidney disease stage G3b) (RR (95% CI): 3.14 (1.56-7.45)). Collectively, these findings indicate that pharmacists and registered sellers need to understand the patient characteristics such as medication history, age, and kidney function when providing non-prescription drugs that contain magnesium oxide. Our findings also highlight the importance of providing information to patients about initial symptoms of hypermagnesemia and appropriate ways to deal with such symptoms.