Natura-LAX 30-Day Dose Powder, 17.9 oz, QC98747 Sale! This item is currently on backorder but you can still purchase it now and we'll ship as soon as more become available. Compare to the Active Ingredient in Miralax. Relieves occasional constipation (irregularity). Softens stool. Once daily dosage. Generally produces a bowel movement in 1 to 3 days. Original prescription strength. Dissolves in any beverage.