See also Warning section.
Drowsiness, dizziness, blurred vision, flushing, headache, nausea, vomiting, constipation, nasal irritation/congestion, trouble sleeping, dry mouth, and sweating may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
To prevent constipation, eat dietary fiber, drink enough water, and exercise. You may also need to take a laxative. Ask your pharmacist which type of laxative is right for you.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Butorphanol can cause withdrawal reactions in people who are physically dependent on opioids. The seriousness of the withdrawal symptoms depends on the level of dependence and the dose of butorphanol. Tell your doctor right away if you develop symptoms such as anxiety, agitation, trouble sleeping, sweating, stomach cramps, and diarrhea.
Tell your doctor right away if you have any serious side effects, including: bleeding from the nose, interrupted breathing during sleep (sleep apnea), mental/mood changes (e.g., anxiety, confusion, hallucinations), fast/slow/irregular heartbeat, severe stomach/abdominal pain, difficulty urinating, signs of your adrenal glands not working well (such as loss of appetite, unusual tiredness, weight loss).
Get medical help right away if you have any very serious side effects, including: difficult/slow/shallow breathing, severe drowsiness/difficulty waking up, seizures.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.