Dexamfetamine and Lisdexamfetamine Exposure With Magnesium Oxide Coadministration
Systemic exposure to amphetamines is not reported as a quantified magnitude (percent change in plasma AUC or Cmax) for magnesium oxide coadministration in the prescribing information for lisdexamfetamine (Vyvanse/Elvanse). [1]
For dexamfetamine (Amfexa), magnesium-containing antacids are not provided with a specific quantified effect on plasma AUC or Cmax in available product information. Amfexa (dexamfetamine) SmPC
Magnesium Oxide Mechanistic Direction of Effect on Amphetamine Exposure
Magnesium oxide acts as a GI alkalinizing agent (antacid effect), and GI alkalinizing agents are expected to increase blood levels of amphetamines. Amfexa (dexamfetamine) SmPC
For lisdexamfetamine (Vyvanse), GI antacids are included under alkalinizing agents, which are described as increasing blood levels and potentiating amphetamine action, with avoidance recommended rather than a numeric AUC/Cmax change provided. [1]
Magnitude of Change in Plasma AUC or Cmax
Lisdexamfetamine (Elvanse/Vyvanse)
- A numerical magnitude (e.g., “X% increase in Cmax” or “Y% increase in AUC”) with magnesium oxide is not provided. [1]
Dexamfetamine (Amfexa)
- A numerical magnitude (e.g., “X% increase in Cmax” or “Y% increase in AUC”) with magnesium oxide is not provided. Amfexa (dexamfetamine) SmPC
Practical Clinical Implication for Reported “Magnitude”
Because no quantified AUC/Cmax ratio specific to magnesium oxide is presented in the available labeling information, the magnitude of increase in systemic amphetamine exposure cannot be expressed numerically from these sources. [1] Amfexa (dexamfetamine) SmPC