Name: Mephobarbital

What should i discuss with my healthcare provider before taking mephobarbital (mebaral)?

Do not take this medication if you are allergic to mephobarbital or to other barbiturates such as amobarbital (Amytal), butabarbital (Butisol), secobarbital (Seconal), or phenobarbital (Luminal, Solfoton).

If you have any of these other conditions, you may need a dose adjustment or special tests to safely use mephobarbital:

  • liver or kidney disease;
  • anemia (lack of red blood cells);
  • heart disease;
  • asthma, chronic obstructive pulmonary disorder (COPD), or other breathing disorder;
  • a history of depression, mental illness, or suicide attempt; or
  • a history of drug or alcohol addiction.

Mephobarbital may be habit-forming and should be used only by the person it was prescribed for. Mephobarbital should never be shared with another person, especially someone who has a history of drug abuse or addiction. Keep the medication in a secure place where others cannot get to it.

FDA pregnancy category D. This medication can cause harm to an unborn baby. It could also cause addiction or withdrawal symptoms in a newborn if the mother takes mephobarbital during late pregnancy. Do not use mephobarbital without your doctor's consent if you are pregnant. Tell your doctor if you become pregnant during treatment. Use an effective form of birth control while you are using this medication.

Mephobarbital can make birth control pills less effective. Ask your doctor about using a non-hormone method of birth control (such as a condom, diaphragm, spermicide) to prevent pregnancy while taking mephobarbital.

Mephobarbital can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

What should i avoid while taking mephobarbital (mebaral)?

Mephobarbital can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert.

Do not drink alcohol while taking mephobarbital. Alcohol can increase the risk of fatal overdose with a barbiturate.

Mephobarbital TABLETS, USP CIV

Rx Only

Mephobarbital - Clinical Pharmacology

Barbiturates are capable of producing all levels of CNS mood alteration from excitation to mild sedation, to hypnosis, and deep coma. Overdosage can produce death. In high enough therapeutic doses, barbiturates induce anesthesia.

Barbiturates depress the sensory cortex, decrease motor activity, alter cerebellar function, and produce drowsiness, sedation, and hypnosis.

Barbiturates are respiratory depressants. The degree of respiratory depression is dependent upon dose. With hypnotic doses, respiratory depression produced by barbiturates is similar to that which occurs during physiologic sleep with slight decrease in blood pressure and heart rate.

Studies in laboratory animals have shown that barbiturates cause reduction in the tone and contractility of the uterus, ureters, and urinary bladder. However, concentrations of the drugs required to produce this effect in humans are not reached with sedative-hypnotic doses.

Barbiturates do not impair normal hepatic function, but have been shown to induce liver microsomal enzymes, thus increasing and/or altering the metabolism of barbiturates and other drugs. (See PRECAUTIONS-Drug Interactions.)

Mephobarbital tablets exerts a strong sedative and anticonvulsant action but has a relatively mild hypnotic effect. It reduces the incidence of epileptic seizures in grand mal and petit mal. Mephobarbital tablets usually causes little or no drowsiness or lassitude. Hence, when it is used as a sedative or anticonvulsant, patients usually become more calm, more cheerful, and better adjusted to their surroundings without clouding of mental faculties. Mephobarbital tablets are reported to produce less sedation than does phenobarbital.

Barbiturates are weak acids that are absorbed and rapidly distributed to all tissues and fluids with high concentrations in the brain, liver, and kidneys. Lipid solubility of the barbiturates is the dominant factor in their distribution within the body.

Barbiturates are bound to plasma and tissue proteins to a varying degree with the degree of binding increasing directly as a function of lipid solubility.

Approximately 50% of an oral dose of Mephobarbital is absorbed from the gastrointestinal tract. Therapeutic plasma concentrations for Mephobarbital have not been established nor has the half-life been determined. Following oral administration, the onset of action of the drug is 30 to 60 minutes and the duration of action is 10 to 16 hours. The primary route of Mephobarbital metabolism is N-demethylation by the microsomal enzymes of the liver to form phenobarbital. Phenobarbital may be excreted in the urine unchanged or further metabolized to p-hydroxyphenobarbital and excreted in the urine as glucuronide or sulfate conjugates. About 75% of a single oral dose of Mephobarbital is converted to phenobarbital in 24 hours.

Therefore, chronic administration of Mephobarbital may lead to an accumulation of phenobarbital (not Mephobarbital) in plasma. It has not been determined whether Mephobarbital or phenobarbital is the active agent during long-time Mephobarbital therapy.

Indications and Usage for Mephobarbital

Mephobarbital tablets are indicated for use as a sedative for the relief of anxiety, tension, and apprehension, and as an anticonvulsant for the treatment of grand mal and petit mal epilepsy.

Adverse Reactions

The following adverse reactions and their incidence were compiled from surveillance of thousands of hospitalized patients. Because such patients may be less aware of the certain milder adverse effects of barbiturates, the incidence of these reactions may be somewhat higher in fully ambulatory patients.

More than 1 in 100 Patients. The most common adverse reactions estimated to occur at a rate of 1 to 3 patients per 100 is:

Nervous System: Somnolence.

Less than 1 in 100 Patients. Adverse reactions estimated to occur at a rate of less than 1 in 100 patients listed below, grouped by organ system, and by decreasing order of occurrence are:

Nervous System: Agitation, confusion, hyperkinesia, ataxia, CNS depression, nightmares, nervousness, psychiatric disturbance, hallucinations, insomnia, anxiety, dizziness, thinking abnormality.

Respiratory System: Hypoventilation, apnea.

Cardiovascular System: Bradycardia, hypotension, syncope.

Digestive System: Nausea, vomiting, constipation.

Other Reported Reactions: Headache, hypersensitivity reactions (angioedema, skin rashes, exfoliative dermatitis), fever, liver damage, megaloblastic anemia following chronic phenobarbital use.


The toxic dose of barbiturates varies considerably. In general, an oral dose of 1 g of most barbiturates produces serious poisoning in an adult. Death commonly occurs after 2 g to 10 g of ingested barbiturate. Barbiturate intoxication may be confused with alcoholism, bromide intoxication, and with various neurological disorders.

Acute overdosage with barbiturates is manifested by CNS and respiratory depression which may progress to Cheyne- Stokes respiration, areflexia, constriction of the pupils to a slight degree (though in severe poisoning they may show paralytic dilation), oliguria, tachycardia, hypotension, lowered body temperature, and coma. Typical shock syndrome (apnea, circulatory collapse, respiratory arrest, and death) may occur.

In extreme overdose, all electrical activity in the brain may cease, in which case a "flat" EEG normally equated with clinical death cannot be accepted. This effect is fully reversible unless hypoxic damage occurs. Consideration should be given to the possibility of barbiturate intoxication even in situations that appear to involve trauma.

Complications such as pneumonia, pulmonary edema, cardiac arrhythmias, congestive heart failure, and renal failure may occur. Uremia may increase CNS sensitivity to barbiturates if renal function is impaired. Differential diagnosis should include hypoglycemia, head trauma, cerebrovascular accidents, convulsive states, and diabetic coma.

Treatment of overdosage is mainly supportive and consists of the following:

  1. Maintenance of an adequate airway, with assisted respiration and oxygen administration as necessary.
  2. Monitoring of vital signs and fluid balance.
  3. If the patient is conscious and has not lost the gag reflex, emesis may be induced with ipecac. Care should be taken to prevent pulmonary aspiration of vomitus. After completion of vomiting, 30 g activated charcoal in a glass of water may be administered.
  4. If emesis is contraindicated, gastric lavage may be performed with a cuffed endotracheal tube in place with the patient in the face down position. Activated charcoal may be left in the emptied stomach and a saline cathartic administered.
  5. Fluid therapy and other standard treatment for shock, if needed.
  6. If renal function is normal, forced diuresis may aid in the elimination of the barbiturate. Alkalinization of the urine increases renal excretion of some barbiturates, including Mephobarbital (which is metabolized to phenobarbital).
  7. Although not recommended as a routine procedure, hemodialysis may be used in severe barbiturate intoxications or if the patient is anuric or in shock.
  8. Patient should be rolled from side to side every 30 minutes.
  9. Antibiotics should be given if pneumonia is suspected.
  10. Appropriate nursing care to prevent hypostatic pneumonia, decubiti aspiration, and other complications of patients with altered states of consciousness.

Mephobarbital Dosage and Administration


Average dose for adults and children 12 years of age and older: 400 mg to 600 mg (6 grains to 9 grains) daily. Mephobarbital tablets are best taken at bedtime if seizures generally occur at night, and during the day if attacks are diurnal.

Treatment should be started with a small dose which is gradually increased over four or five days until the optimum dosage is determined. If the patient has been taking some other antiepileptic drug, it should be tapered off as the doses of Mephobarbital tablets are increased, to guard against the temporary marked attacks that may occur when any treatment for epilepsy is changed abruptly. Similarly, when the dose is lowered to a maintenance level or to be discontinued, the amount should be, reduced gradually over four or five days.

Special Patient Population

Dosage should be reduced in the elderly or debilitated because these patients may be more sensitive to barbiturates. Dosage should be reduced for patients with impaired renal function or hepatic disease.

Combination with Other Drugs

Mephobarbital tablets may be used in combination with phenobarbital, either in the form of alternating courses or concurrently. When the two drugs are used at the same time, the dose should be about one-half the amount of each used alone. The average daily dose for an adult is from 50 mg to 100 mg (3/4 grain to 1 1/2 grains) of phenobarbital and from 200 mg to 300 mg (3 grains to 4 1/2 grains) of Mephobarbital tablets.

Mephobarbital tablets may also be used with phenytoin sodium; in some cases, combined therapy appears to give better results than either agent used alone, since phenytoin sodium is particularly effective for the psychomotor types of seizure but relatively ineffective for petit mal. When the drugs are employed concurrently, a reduced dose of phenytoin sodium is advisable, but the full dose of Mephobarbital tablets may be given. Satisfactory results have been obtained with an average daily dose of 230 mg (3 1/2 grains) of phenytoin sodium plus about 600 mg (9 grains) of Mephobarbital tablets.


Adults: 32 mg to 100 mg (1/2 grain to 1 1/2 grains)–optimum dose, 50 mg (3/4 grain)–three to four times daily.