This medication is used alone or with other medications to control seizures. Controlling and reducing seizures lets you do more of your normal daily activities, reduces your risk of harm when you lose consciousness, and lessens your risk for a possibly life-threatening condition of frequent, repeated seizures. Phenobarbital belongs to a class of drugs known as barbiturate anticonvulsants/hypnotics. It works by controlling the abnormal electrical activity in the brain that occurs during a seizure. This medication is also used for a short time (usually no more than 2 weeks) to help calm you or help you sleep during periods of anxiety. It works by affecting certain parts of the brain to cause calming.
How to use Phenobarbital
Take this medication by mouth with or without food, usually once daily at bedtime for seizure control, or as directed by your doctor. Take with food or milk if stomach upset occurs. If you are using the liquid form of this medication, measure the dose carefully using a special measuring device/cup. Do not use a household spoon because you may not get the correct dose.
Dizziness, drowsiness, excitation, headache, tiredness, loss of appetite, nausea, or vomiting may occur as your body adjusts to the medication. 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.
A small number of people who take anticonvulsants for any condition (such as seizure, bipolar disorder, pain) may experience depression, suicidal thoughts/attempts, or other mental/mood problems. Tell your doctor right away if you or your family/caregiver notice any unusual/sudden changes in your mood, thoughts, or behavior including signs of depression, suicidal thoughts/attempts, thoughts about harming yourself.
Tell your doctor right away if you have any serious side effects, including: staggering walk/clumsiness, double vision, fast/slow/shallow breathing, fainting, slow heartbeat, severe tiredness/weakness, pale skin.
Before taking phenobarbital, tell your doctor or pharmacist if you are allergic to it; or to other barbiturates (such as primidone, secobarbital); or to other anti-seizure medications (such as carbamazepine, fosphenytoin, oxcarbazepine, phenytoin); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: certain hormone problems (adrenal disease such as Addison’s disease), liver problems, kidney problems, lung disease (such as sleep apnea, chronic obstructive pulmonary disease–COPD), mental/mood disorders (such as depression, thoughts of suicide), personal or family history of a substance use disorder (such as overuse of or addiction to drugs/alcohol), personal/family history of a certain blood disorder (porphyria), certain vitamin deficiencies (folic acid, vitamin K).
This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana
Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor’s approval.
Other medications can affect the removal of phenobarbital from your body, which may affect how phenobarbital works. Examples include St. John’s wort, among others.
This medication can speed up the removal of other medications from your body, which may affect how they work. Examples of affected drugs include artemether/lumefantrine, asunaprevir, atazanavir, boceprevir, cobicistat, lurasidone, ranolazine, sofosbuvir, sorafenib, voriconazole, certain calcium channel blockers such as felodipine/nimodipine, among others.
If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe tiredness/dizziness, inability to wake up, very slow breathing rate.
Do not share this medication with others. Sharing it is against the law.
Keep all medical appointments so that your doctor can monitor your progress or check for side effects. For long-term use, laboratory and/or medical tests (such as phenobarbital blood levels, blood counts, liver/kidney tests) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.