Phenobarbital

This information from Lexicomp^® explains what you need to know about this medication, including what it’s used for, how to take it, its side effects, and when to call your healthcare provider.

Brand Names: US

Sezaby

What is this drug used for?

• It is used to help control certain kinds of seizures.
• It is used to treat anxiety.
• It is used to treat sleep problems.
• It may be given to you for other reasons. Talk with the doctor.

What do I need to tell my doctor BEFORE I take this drug?

All products:

• If you are allergic to this drug; any part of this drug; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
• If you have any of these health problems: A block in the airway, liver disease, or shortness of breath.
• If you have ever had porphyria.
• If you have any of these health problems: Heart problems like heart failure or a certain type of chest pain (unstable angina), slow or abnormal heartbeat (like long QT on ECG), kidney disease, low thyroid function, or a very narrow heart valve (aortic stenosis).
• If you have had a recent heart attack.
• If you are taking any drugs that can cause a certain type of heartbeat that is not normal (prolonged QT interval). There are many drugs that can do this. Ask your doctor or pharmacist if you are not sure.

Injection:

• If the patient is a newborn or infant. Some products may have benzyl alcohol. In large amounts, benzyl alcohol may cause severe and sometimes deadly side effects in newborns or infants. The doctor may decide the benefits of taking this drug outweigh the risks. Talk with the doctor if you have questions about giving this drug to your child.

This is not a list of all drugs or health problems that interact with this drug.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take this drug with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take this drug?

For all uses of this drug:

• Tell all of your health care providers that you take this drug. This includes your doctors, nurses, pharmacists, and dentists.
• The risk of dependence and withdrawal are raised the longer you take this drug and the higher the dose. Talk to your doctor before you lower the dose or stop this drug. You will need to follow your doctor’s instructions. Lowering the dose or stopping this drug all of a sudden may cause withdrawal. This can be life-threatening. Get medical help right away if you have any bad effects.
• If you have been taking this drug for a long time or at high doses, it may not work as well and you may need higher doses to get the same effect. This is known as tolerance. Call your doctor if this drug stops working well. Do not take more than ordered.
• Have your blood work checked if you are on this drug for a long time. Talk with your doctor.
• Avoid driving and doing other tasks or actions that call for you to be alert until you see how this drug affects you.
• Avoid drinking alcohol while taking this drug.
• Talk with your doctor before you use marijuana, other forms of cannabis, or prescription or OTC drugs that may slow your actions.
• Like other drugs that may be used for seizures, this drug may rarely raise the risk of suicidal thoughts or actions. The risk may be higher in people who have had suicidal thoughts or actions in the past. Call the doctor right away about any new or worse signs like depression; feeling nervous, restless, or grouchy; panic attacks; or other changes in mood or behavior. Call the doctor right away if any suicidal thoughts or actions occur.
• If you are 65 or older, use this drug with care. You could have more side effects.
• If the patient is a child, use this drug with care. The risk of some side effects may be higher in children.
• Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use 2 kinds of birth control while taking this drug.
• This drug may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking this drug, call your doctor right away.
• Taking this drug in the third trimester of pregnancy may lead to withdrawal in the newborn. Talk with the doctor.
• Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

For seizures:

• If seizures are different or worse after starting this drug, talk with the doctor.

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

All products:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Feeling confused.
• Change in balance.
• Muscle spasm.
• Bad dreams.
• Restlessness.
• Hallucinations (seeing or hearing things that are not there).
• Shortness of breath.
• Slow heartbeat.
• Feeling very tired or weak.
• Severe dizziness or passing out.
• A severe skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may happen. It can cause severe health problems that may not go away, and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.
• A severe and sometimes deadly effect has happened in people taking drugs for seizures like this drug. Call your doctor right away if you have swollen glands; fever; rash; painful sores in the mouth or around the eyes; chest pain; signs of kidney problems like unable to pass urine or change in the amount of urine passed; or signs of liver problems like dark urine, tiredness, decreased appetite, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.

Injection (if given in the vein):

• Some health problems may happen when this drug is given too fast. This includes trouble breathing or signs of high or low blood pressure like very bad headache or dizziness, passing out, or change in eyesight. Tell your doctor right away if you have any of these signs.
• This drug may cause tissue damage if the drug leaks from the vein. Tell your nurse if you have any redness, burning, pain, swelling, blisters, skin sores, or leaking of fluid where the drug is going into your body.

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

All products:

• Feeling dizzy or sleepy.
• Headache.
• Upset stomach or throwing up.
• Constipation.
• Feeling nervous and excitable.
• Trouble sleeping.

Injection:

• Irritation where the shot is given.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to your national health agency.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

How is this drug best taken?

Use this drug as ordered by your doctor. Read all information given to you. Follow all instructions closely.

All oral products:

• Take with or without food. Take with food if it causes an upset stomach.

Liquid:

• Measure liquid doses carefully. Use the measuring device that comes with this drug. If there is none, ask the pharmacist for a device to measure this drug.

Injection:

• It is given as a shot into a muscle or vein.

What do I do if I miss a dose?

All oral products:

• Take a missed dose as soon as you think about it.
• If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
• Do not take 2 doses at the same time or extra doses.

Injection:

• Call your doctor to find out what to do.

How do I store and/or throw out this drug?

All oral products:

• Store at room temperature protected from light. Store in a dry place. Do not store in a bathroom.
• Keep lid tightly closed.

Injection:

• If you need to store this drug at home, talk with your doctor, nurse, or pharmacist about how to store it.

All products:

• Store this drug in a safe place where children cannot see or reach it, and where other people cannot get to it. A locked box or area may help keep this drug safe. Keep all drugs away from pets.
• Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.

General drug facts

• If your symptoms or health problems do not get better or if they become worse, call your doctor.
• Do not share your drugs with others and do not take anyone else’s drugs.
• Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
• Some drugs may have another patient information leaflet. Check with your pharmacist. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
• If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

Consumer Information Use and Disclaimer

This generalized information is a limited summary of diagnosis, treatment, and/or medication information. It is not meant to be comprehensive and should be used as a tool to help the user understand and/or assess potential diagnostic and treatment options. It does NOT include all information about conditions, treatments, medications, side effects, or risks that may apply to a specific patient. It is not intended to be medical advice or a substitute for the medical advice, diagnosis, or treatment of a health care provider based on the health care provider’s examination and assessment of a patient’s specific and unique circumstances. Patients must speak with a health care provider for complete information about their health, medical questions, and treatment options, including any risks or benefits regarding use of medications. This information does not endorse any treatments or medications as safe, effective, or approved for treating a specific patient. UpToDate, Inc. and its affiliates disclaim any warranty or liability relating to this information or the use thereof. The use of this information is governed by the Terms of Use, available at https://www.wolterskluwer.com/en/know/clinical-effectiveness-terms.

Last Reviewed Date

2023-01-18

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