You should experience relief in six to eight hours. In addition, if you take other medications, mineral oil may interfere with their absorption. Wait at least two hours after taking mineral oil to take other medications, and vice versa. Saline laxatives change the salt balance in the digestive tact, the Graedons explain. They draw water into your stool, which adds bulk and stimulates peristalsis.
Milk of magnesia is the best-known saline laxative.
It usually works in one to six hours. The recommended dose depends on your age. Read the package directions. Milk of magnesia should not be used for extended periods, according to the APA, because large doses of magnesium may cause muscle weakness, and a potentially serious drop in blood pressure. Stool softeners .