Natura-LAX 14-Day Dose Powder, 8.3 oz, QC95981 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. Generally produces a bowel movement in 1 to 3 days. Once daily dose. Original prescription strength. Dissolves in any beverage.