Sorbitol is an osmotic agent.
Osmotic agents work by pulling large amounts of water into the the large intestine making the stools soft and loose.
These laxatives work within 3 hours and are useful for treating constipation rather than for preventing it.
WHen was your last bowel movement?
Have you eaten much?
Sometimes depending on how much you are backed up it could take until tomorrow. You could always try an enema if there is no medical reason that you shouldn't. You can buy them at the drug store .