Unwanted sleepiness, trouble waking up, dizziness, excitation, headache, tiredness, loss of appetite, nausea, or vomiting may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly. 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. Tell your doctor immediately if any of these unlikely but serious side effects occur: mental/mood changes (such as agitation, confusion, depression, hallucinations, thoughts of suicide, nightmares), slurred speech, staggering walk/clumsiness, double vision, memory problems. Rarely, after taking this drug, people have gotten out of bed and driven vehicles while not fully awake ("sleep-driving"). People have also sleepwalked, or have prepared/eaten food, made phone calls, or had sex while not fully awake. Often these people do not remember these events. If you discover that you have done any of these things, tell your doctor immediately. Drinking alcohol, taking other medications that cause drowsiness, or taking higher doses of butabarbital may increase your risk for this effect. Do not drink alcohol while using this medication. Tell your doctor immediately if any of these rare but very serious side effects occur: slow/shallow breathing, fainting, slow heartbeat. A very serious allergic reaction to this drug is rare. However, seek immediate medical attention 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. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.