Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Breathing: Phenobarbital can suppress breathing. People at risk for breathing difficulties, such as asthma, should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Drowsiness/reduced alertness: Barbiturates such as phenobarbital may reduce the mental and physical abilities needed for tasks such as driving a car or operating machinery. Drinking alcohol at the same time may have an additive effect. People taking this medication may be more likely to experience broken bones due to falls. This applies especially to seniors.
Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.
If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.
Skin rash: Rarely, people taking phenobarbital experience a severe skin reaction that can be life-threatening. If you experience a rash that gets worse, or develops into blisters, sores on the lips or eyes or covers a large area of the body, with or without fever, contact your doctor immediately.
Stopping the medication: If this medication needs to be stopped, it should be done gradually, under the supervision of your doctor. Suddenly stopping phenobarbital can cause a return of seizures that are difficult to control.
Suicidal or agitated behaviour: People with epilepsy sometimes experience depression. This can increase your risk of feeling agitated (restless, anxious, aggressive, emotional, and feeling not like themselves), or wanting to hurt themselves or others. If you experience these side effects or notice them in a family member who is taking this medication, contact your doctor immediately.
Withdrawal: Barbiturates such as phenobarbital may become habit-forming (physical and psychological dependence) if used for long periods of time. Withdrawal symptoms after prolonged use include:
- loss of appetite
- weight loss
People stopping this medication after having taken it for long periods of time should reduce the dose gradually under a doctor's supervision.
Pregnancy: Medications used to prevent major seizures should not be stopped. The use of this medication is not recommended during pregnancy. However, the decision about whether or not to stop the medication must weigh the potential benefits against the potential risks. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking phenobarbital, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.