MiraLax is the brand name for the generic drug polyethylene glycol , a laxative used to treat occasional constipation. The drug works by bringing water into the bowels, which helps keep the digestive system regular. Stool becomes softer when the bowels retain water. MiraLax typically relieves constipation in one to three days. Should parents be concerned about MiraLAX side “MiraLAX is a safe and effective osmotic It is approved and labeled for use in adults and children 17 Founded: Sep 18, All it says: “MiraLAX® is safe and effective – and available without a prescription. ” The cutout from “What Is MiraLAX” product brochure. How can Merck get away claiming that MiraLAX is “safe” and “without harsh side effects?” Well, just like it did with Vioxx, another presumably “safe” miracle drug.