Phenobarbital - Side Effects | Dose

Phenobarbital belongs to the group of medicines referred to as anti-epileptics, and is used for the treatment of epilepsy except absans.

Do not take this medicine if you have

  • allergy (hypersensitivity) on the phenobarbital or other barbiturates,
  • porphyria (a hereditary disorder of the metabolism of the red blood pigment, hemoglobin);
  • severe difficulty breathing;
  • severe liver and kidney disease;

The medicine should not be administered simultaneously with other central nervous system depressants, including alcohol!

Warning and precautions

Talk to your doctor or pharmacist before you start taking this medicine if:

  • You are young, slowed mental activity, elderly, or have had problems with the abuse of certain medicines or alcohol;
  • you have kidney or liver disorders;
  • have difficulty breathing;
  • suffer from severe and long-lasting pain

Tell your doctor if you have side effects such as suicide attempt or suicide ideation!

Use with other medicines (interactions)

Please note that this information may relate to the medicines that you longer apply, and the medicines that you are planning to apply in the future. Tell your doctor if you are taking or have recently applied any other medicines including medicines obtained without a prescription. Phenorbarbital speeds metabolism of many other medicines. Tell your doctor or pharmacist if you are taking or have recently taken the following medicines:

  • Warfarin
  • Antiepileptic medicines such as:phenytoin, carbamazepine, oxcarbazepine, lamotrigine, valproic acid, vigabatrin
  • Methadone
  • Antibiotics such as: rifampin, doxycycline, metronidazole, chloramphenicol, griseofulvin, itraconazole, voriconazole, abacavir, indinavir, nelfinavir, lopinavir
  • MAO inhibitors ( phenelzine, moclobemide)
  • Paroxetin
  • Antidepressants such as: imipramine, trimipramine, desipramine
  • Antipsychotic medicines such as: clonazepam, tioridazine, chlorpromazine, haloperidol
  • Antihypertensive medicines such as: diltiazem, verapamil, propranolol, nifedipine, nicardipine, metoprolol, timolol
  • Digoxin
  • Irinotecan
  • Etoposide
  • Hydrocortisone
  • Prednisolone
  • Folic acid
  • Vitamin D
  • Antiasthmatic medicines such as: montelukast, theophylline
  • Contraceptives
  • Memantine

Please note that this list is not complete! Inform your doctor if you are taking any other medicines ! Do not use alcohol while taking phenobarbital . Alcohol can worsen your symptoms or side effects! Taking food and liquid with phenobarnital does not change effect of this medicine.

Taking this medicine during the pregnancy

If you are pregnant or plan to become pregnant, you should talk with your doctor before you start taking phenobarbital. If you become pregnant while taking this medicine, the doctor will tell you whether to proceed therapy or any other medicine suitable during pregnancy. Do not stop taking the medicine before talk to your doctor, because it may lead to disease exacerbation. If taking the medicine during pregnancy (especially over the first three and the last 3 months) may occur abnormalities of the fetus. Also, the medicine can cause bleeding in the baby when it is born. Your doctor may decide that it is very important to continue taking the medicine. He will explain the risks arising from use of the medicine during gestation. Before you start to use folic acid check with your doctor because it interacts with phenobarbital, which will require adjusting the dosage. Since this medicine is excreted into breast milk and may cause drowsiness in your baby, so the breastfeeding is not recommended.

The effect of this medicine on the management of motor vehicles and machinery operation

The medicine has a strong influence on the ability of management of motor vehicles and during therapy is not allowed drive a motor or work with machinery!

How to use this medicine

The medicine is administered orally. Take the medicine as recommended by your doctor. The usual dose for adults and children aged 12-18 years is 60-180 mg once daily in the evening. The usual maintenance dose for children aged 1 month to 12 years 2,5 - 4 mg / kg once or twice daily. In elderly patients a doctor may prescribe a lower dose of the medicine.


If you apply more than the prescribed dose is, consult your doctor or pharmacist! In case of overdose can occur drowsiness, coma, difficulty breathing, low blood pressure, shock, followed by renal impairment, a reduction in body temperature and the characteristic hemorrhagic bullae (blisters on the skin filled blood). Length and depth of the depression of the CNS depends on the dosage and tolerance of the patient.

If you forget to take the medicine

If you forget to take medication on time, do not use double dose later. Simply continue to use the medicine according to the usual schedule. If you forget to take a dose, take the medication as soon as possible.

If you suddenly stop taking phenobarbital

Do not suddenly stop taking this medication because it is possible to occur side effects such as: tremor, dizziness, insomnia, headache,delirium, vertigo. If you want to stop the use of phenobarbital it is necessary to consult your doctor to help you gradually decreasing the dosage.

Side effects

Contact your doctor if you have any of this side effects Effects on the nervous system: difficulty in thinking, unusual excitement, visions of things that are not there, disorder memory, hyperactivity, drowsiness, lethargy, irregular movements and recoil eye movements as well as behavioral disorders and confusion in elderly patients. Effects on the lungs: shortness of breath. Effects on skin: In 1-2 % of patients allergic skin reactions occur (rash) and rarely erythema multiforme, exfoliative dermatitis and toxic epidermal necrolysis, skin disorders that can lead to death. Therefore, if the spot changes the skin during treatment, contact your doctor for advice. Effects on blood: medicine may cause a disease of the blood by the presence of immature red blood cells in the circulation (megaloblastic anemia), as well as agranulocytosis (decrease in the number of white blood cells) or thrombocytopenia (decrease of platelet count). If you notice an increased number of bruises, nosebleeds, frequent sore throat or infection, you need to tell your doctor. Other effects: hepatitis (liver inflammation), cholestasis, hypotension (low blood pressure),rachitis and deformities bones (osteomalacia). As a rare adverse reactions may occur antiepileptic hypersensitivity syndrome (AHS). It is idiosyncratic medicine-induced side effects may be manifested in some patients to antiepileptic therapy (phenytoin, carbamazepine, phenobarbital and lamotrigine), which is characterized by fever, rash, lymphadenopathy (swollen lymph nodes), swelling of the face, impaired liver function, and disturbances of all lineages of blood cells, usually performances in the first two months of therapy. This syndrome may have a different clinical picture, and in some cases can lead to the development of disseminated intravascular coagulation (clotting system disorder), and impairment of the function of a number of organs. Early signs of hypersensitivity (e.g., fever and lymphadenopathy) may occur without side- reactions of the skin. Acute disorders of the liver, such as impaired function, hepatitis, magnification of the liver and elevated serum transaminase levels in the blood have been reported in rare cases of AHS 's. The impact on the liver may be transient, but there is report of cases with fatal outcome.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.