The most common side effects are difficulty sleeping, dry mouth, headache, dizziness, anxiety and nausea. To reduce sleeping problems, it's best to take your evening tablet at least four hours before bedtime (but remember, you must leave eight hours between tablets).
The most serious side effect is the risk of seizure, which is estimated to occur in about one in 1000 patients (0.1%). Your doctor will ask you a series of questions to determine if you are at risk from seizure. If you have a seizure, stop taking Zyban and seek medical attention immediately.
A small number of people (about one to three per 1000 patients) have had allergic reactions to bupropion. These include itching, hives, skin wheals, or breathlessness. There have been a few cases of fever, joint and muscle pain occurring with skin rash, and these can occur 10 to 20 days after starting treatment. If you think you are having an allergic reaction to bupropion, stop taking it and tell your doctor immediately. If that is not possible, you should go to the casualty department at your nearest hospital.
A small number of users of Zyban may develop mental health problems, such as depression and suicidal or self-harming behaviour. Symptoms are more likely to occur early in the treatment. Family members should be alert for unusual changes in behaviour or mood. You should seek medical advice as soon as possible if you have any symptoms that concern you. Zyban may worsen symptoms in people with certain types of mental illness, so it is important to discuss your history with your doctor before taking Zyban.
If your doctor has directed you to use Zyban and a nicotine replacement product at the same time, it is recommended that your blood pressure be monitored.
You should talk to your doctor if you have any side effects, including any not mentioned here, which cause you concern. The Consumer Medicine Information has more details on side effects, which is important to read.
Serious side effects of Zyban are rare. However, it is important to use Zyban correctly, with your doctor's supervision. You can lower your risk by making sure you are not in a high risk group for seizure and checking with your doctor before using any other medicine. Also, do not take more than one tablet within eight hours, be sure to swallow the tablet whole, and limit your use of alcohol (Read Using Zyban section).
Read the Consumer Medicine Information and keep it until you've finished using the medicine. Never use any medicine that has been prescribed for somebody else.
Taking too many tablets of Zyban can cause serious side effects, including rapid heart beat and seizures. Other effects of overdose include lethargy, confusion and tremors. If you think that you or someone else may have taken too many tablets, call your doctor or the Poisons Information Centre (131126) for advice, even if there does not appear to be any effects. Then, go to hospital. If you suspect a child has taken Zyban, follow the advice above.