Acetaminophen does not cause these side effects, but high doses of it can hurt the liver. Opioids may cause constipation, sleepiness, nausea, problems with urination or itching. They may also slow breathing, especially when they are first given, but this is unusual in people who take opioids on a regular basis for pain. Most side effects from opioid pain medicines happen in the first few hours of treatment and gradually go away. The best way to prevent constipation is to drink lots of water, juice, and other liquids, and to eat more fruits and vegetables.
Exercise also helps to prevent constipation.
Your doctor or nurse may also be able to give you a stool softener or a laxative. Nausea and vomiting . When this happens, it usually only lasts for the first day or two after starting a medicine. Tell your doctors and nurses about any nausea or vomiting. They can give you medicine to stop these side effects.