Metoclopramide 常用於新生兒吐溢奶，但可能誘發罕見卻嚴重的變性血紅素血症。由於以往文獻多為過量使用 metoclopramide，這次分享兩個案例使用正常略高劑量的 metoclopramide，發生藥品相關變性血紅素血症的不良反應，同時討論變性血紅素血症治療方式。個案一是 14 天大的女嬰，出生第 5 天開始使用 metoclopramide 0.2 mg/kg q6h，用藥 9 天後 methemoglobin 數值高達 19.6%，停藥 1 天後數值降至 13.4%。個案二是 11 天大的男嬰，出生第 3 天開始使用相同劑量，用藥 8 天後methemoglobin 數值高達 10.2%，停藥 3 天後數值降至 2.1%，停藥 7 天後降至 1.4%。新生兒肝腎臟功能未發育完全，較成人更易誘發變性血紅素血症，而 metoclopramide是常見誘發的藥物，若必須使用，建議由較低劑量開始，並依症狀改善程度及早停用藥物，以減少藥物相關變性血紅素血症的發生機會。

Metoclopramide is a commonly used drug to treat gastroesophageal reflux disease in infants, but it may induce rare but severe methemoglobinemia. The previous literature mostly described overdose of metoclopramide. In this article, we report two cases in our hospital, and metoclopramide brings the side effect of drug-related methemoglobinemia at slightly above the normal therapeutic dose. Herein, we discuss the clinical features and treatment of metoclopramide-induced methemoglobinemia. Case 1 is a 14-day-old girl who started using metoclopramide 0.2 mg/kg q6h on the 5th day of birth. The value of methemoglobin reached 19.6% after 9 days of treatment, and fell to 13.4% after 1 day of discontinuation. Case 2 is an 11-day-old boy who started using the same dose on the 3rd day of birth. After 8 days of treatment, the value of methemoglobin reached 10.2%, dropped to 2.1% after 3 days of discontinuation, and 1.4% after 7 days of discontinuation. Neonate’s liver and kidney function are not well developed, and methemoglobinemia is more likely to be induced than adults. Metoclopramide is one of the high-risk drugs, and therefore, it is recommended to initiate at a lower dose and stop when patients have symptoms to reduce the incidence of drug-related methemoglobinemia.