Atrium

Phenobarbital:

• Indications and usage
• Contraindications
• Warnings
• Precautions
• Adverse reactions
• Drug abuse and dependence
• Overdosage
• Dosage and administration
• How supplied
• Atrium (Phenobarbital) reviews

INDICATIONS AND USAGE

• Sedative
• Anticonvulsant – For the treatment of generalized and partial seizures.

CONTRAINDICATIONS

Atrium (Phenobarbital) is contraindicated in patients who are hypersensitive to barbiturates, in patients with a history of manifest or latent porphyria, and in patients with marked impairment of liver function or respiratory disease in which dyspnea or obstruction is evident.

WARNINGS

• Habit Forming. Atrium (Phenobarbital) may be habit forming. Tolerance and psychological and physical dependence may occur with continued use (see DRUG ABUSE AND DEPENDENCE and Pharmacokinetics under CLINICAL PHARMACOLOGY). Patients who have psychologic dependence on barbiturates may increase the dosage or decrease the dosage interval without consulting a physician and may subsequently develop a physical dependence on barbiturates. In order to minimize the possibility of overdosage or the development of dependence, the prescribing and dispensing of sedative-hypnotic barbiturates should be limited to the amount required for the interval until the next appointment. Abrupt cessation after prolonged use in a person who is dependent on the drug may result in withdrawal symptoms, including delirium, convulsions, and possibly death. Barbiturates should be withdrawn gradually from any patient known to be taking excessive doses over long periods of time (see DRUG ABUSE AND DEPENDENCE ).
• Acute or Chronic Pain. Caution should be exercised when barbiturates are administered to patients with acute or chronic pain, because paradoxical excitement could be induced or important symptoms could be masked. However, the use of barbiturates as sedatives in the postoperative surgical period and as adjuncts to cancer chemotherapy is well established.
• Usage in Pregnancy. Barbiturates can cause fetal damage when administered to a pregnant woman. Retrospective, case-controlled studies have suggested a connection between the maternal consumption of barbiturates and a higher than expected incidence of fetal abnormalities. Barbiturates readily cross the placental barrier and are distributed throughout fetal tissues; the highest concentrations are found in the placenta, fetal liver, and brain. Fetal blood levels approach maternal blood levels following parenteral administration. Withdrawal symptoms occur in infants born to women who receive barbiturates throughout the last trimester of pregnancy (see DRUG ABUSE AND DEPENDENCE ). If Atrium (Phenobarbital) is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.
• Usage in Pediatric Patients. Atrium (Phenobarbital) has been reported to be associated with cognitive deficits in children taking it for complicated febrile seizures.
• Synergistic Effects. The concomitant use of alcohol or other CNS depressants may produce additive CNS depressant effects.

PRECAUTIONS

General

Barbiturates may be habit forming. Tolerance and psychological and physical dependence may occur with continued use. Barbiturates should be administered with caution, if at all, to patients who are mentally depressed, have suicidal tendencies, or have a history of drug abuse.

Elderly or debilitated patients may react to barbiturates with marked excitement, depression, or confusion. In some persons, especially children, barbiturates repeatedly produce excitement rather than depression.

In patients with hepatic damage, barbiturates should be administered with caution and initially in reduced doses. Barbiturates should not be administered to patients showing the premonitory signs of hepatic coma.

The systemic effects of exogenous and endogenous corticosteroids may be diminished by Atrium (Phenobarbital). Thus, this product should be administered with caution to patients with borderline hypoadrenal function, regardless of whether it is of pituitary or of primary adrenal origin.

Information for Patients

The following information and instructions should be given to patients receiving barbiturates.

• The use of barbiturates carries with it an associated risk of psychological and/or physical dependence. The patient should be warned against increasing the dose of the drug without consulting a physician.
• Barbiturates may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a car or operating machinery. The patient should be cautioned accordingly.
• Alcohol should not be consumed while taking barbiturates. The concurrent use of the barbiturates with other CNS depressants (e.g., alcohol, narcotics, tranquilizers, and antihistamines) may result in additional CNS-depressant effects.

Laboratory Tests

Prolonged therapy with barbiturates should be accompanied by periodic laboratory evaluation of organ systems, including hematopoietic, renal, and hepatic systems.

Drug Interactions

Most reports of clinically significant drug interactions occurring with the barbiturates have involved Atrium (Phenobarbital). However, the application of these data to other barbiturates appears valid and warrants serial blood level determinations of the relevant drugs when there are multiple therapies.

• Anticoagulants. Atrium (Phenobarbital) lowers the plasma levels of dicumarol and causes a decrease in anticoagulant activity as measured by the prothrombin time. Barbiturates can induce hepatic microsomal enzymes resulting in increased metabolism and decreased anticoagulant response of oral anticoagulants (e.g., acenocoumarol, warfarin, dicumarol, and phenprocoumon). Patients stabilized on anticoagulant therapy may require dosage adjustments if barbiturates are added to or withdrawn from their dosage regimen.
• Corticosteroids. Barbiturates appear to enhance the metabolism of exogenous corticosteroids, probably through the induction of hepatic microsomal enzymes. Patients stabilized on corticosteroid therapy may require dosage adjustments if barbiturates are added to or withdrawn from their dosage regimen.
• Griseofulvin. Atrium (Phenobarbital) appears to interfere with the absorption of orally administered griseofulvin, thus decreasing its blood level. The effect of the resultant decreased blood levels of griseofulvin on therapeutic response has not been established. However, it would be preferable to avoid concomitant administration of these drugs.
• Doxycycline. Atrium (Phenobarbital) has been shown to shorten the half-life of doxycycline for as long as 2 weeks after barbiturate therapy is discontinued. This mechanism is probably through the induction of hepatic microsomal enzymes that metabolize the antibiotic. If Atrium (Phenobarbital) and doxycycline are administered concurrently, the clinical response to doxycycline should be monitored closely.
• Phenytoin, Sodium Valproate, Valproic Acid. The effect of barbiturates on the metabolism of phenytoin appears to be variable. Some investigators report an accelerating effect, whereas others report no effect. Because the effect of barbiturates on the metabolism of phenytoin is not predictable, phenytoin and barbiturate blood levels should be monitored more frequently if these drugs are given concurrently. Sodium valproate and valproic acid increase the Atrium (Phenobarbital) serum levels; therefore, Atrium (Phenobarbital) blood levels should be closely monitored and appropriate dosage adjustments made as clinically indicated.
• CNS Depressants. The concomitant use of other CNS depressants, including other sedatives or hypnotics, antihistamines, tranquilizers, or alcohol, may produce additive depressant effects.
• Monoamine Oxidase Inhibitors (MAOIs). MAOIs prolong the effects of barbiturates, probably because metabolism of the barbiturate is inhibited.
• Estradiol, Estrone, Progesterone, and other Steroidal Hormones. Pretreatment with or concurrent administration of Atrium (Phenobarbital) may decrease the effect of estradiol by increasing its metabolism. There have been reports of patients treated with antiepileptic drugs (e.g., Atrium (Phenobarbital)) who become pregnant while taking oral contraceptives. An alternate contraceptive method might be suggested to women taking Atrium (Phenobarbital).

Carcinogenesis

• Animal Data. Atrium sodium is carcinogenic in mice and rats after lifetime administration. In mice, it produced benign and malignant liver cell tumors. In rats, benign liver cell tumors were observed very late in life.
• Human Data. In a 29-year epidemiological study of 9,136 patients who were treated on an anticonvulsant protocol that included Atrium (Phenobarbital), results indicated a higher than normal incidence of hepatic carcinoma. Previously, some of these patients had been treated with thorotrast, a drug which is known to produce hepatic carcinomas. Thus, this study did not provide sufficient evidence that Atrium (Phenobarbital) sodium is carcinogenic in humans.

A retrospective study of 84 children with brain tumors matched to 73 normal controls and 78 cancer controls (malignant disease other than brain tumors) suggested an association between exposure to barbiturates prenatally and an increased incidence of brain tumors.

Usage in Pregnancy

• Teratogenic Effects. Pregnancy Category D – See Usage in Pregnancy under WARNINGS.
• Nonteratogenic Effects. Reports of infants suffering from long-term barbiturate exposure in utero included the acute withdrawal syndrome of seizures and hyperirritability from birth to a delayed onset of up to 14 days (see DRUG ABUSE AND DEPENDENCE ).

Labor and Delivery

Hypnotic doses of barbiturates do not appear to impair uterine activity significantly during labor. Full anesthetic doses of barbiturates decrease the force and frequency of uterine contractions. Administration of sedative-hypnotic barbiturates to the mother during labor may result in respiratory depression in the newborn. Premature infants are particularly susceptible to the depressant effects of barbiturates. If barbiturates are used during labor and delivery, resuscitation equipment should be available.

Data are not available to evaluate the effect of barbiturates when forceps delivery or other intervention is necessary or to determine the effect of barbiturates on the later growth, development, and functional maturation of the child.

Nursing Mothers

Caution should be exercised when Atrium (Phenobarbital) is administered to a nursing woman, because small amounts of barbiturates are excreted in the milk.

ADVERSE REACTIONS

The following adverse reactions have been reported:

CNS Depression – Residual sedation or “hangover”, drowsiness, lethargy, and vertigo. Emotional disturbances and phobias may be accentuated. In some persons, barbiturates such as Atrium (Phenobarbital) repeatedly produce excitement rather than depression, and the patient may appear to be inebriated. Irritability and hyperactivity can occur in children. Like other nonanalgesic hypnotic drugs, barbiturates such as Atrium (Phenobarbital), when given in the presence of pain, may cause restlessness, excitement, and even delirium. Rarely, the use of barbiturates results in localized or diffuse myalgic, neuralgic, or arthritic pain, especially in psychoneurotic patients with insomnia. The pain may appear in paroxysms, is most intense in the early morning hours, and is most frequently located in the region of the neck, shoulder girdle, and upper limbs. Symptoms may last for days after the drug is discontinued.

Respiratory/Circulatory – Respiratory depression, apnea, circulatory collapse.

Allergic – Acquired hypersensitivity to barbiturates consists chiefly in allergic reactions that occur especially in persons who tend to have asthma, urticaria, angioedema, and similar conditions. Hypersensitivity reactions in this category include localized swelling, particularly of the eyelids, cheeks, or lips, and erythematous dermatitis. Rarely, exfoliative dermatitis (e.g., Stevens-Johnson syndrome and toxic epidermal necrolysis) may be caused by Atrium (Phenobarbital) and can prove fatal. The skin eruption may be associated with fever, delirium, and marked degenerative changes in the liver and other parenchymatous organs. In a few cases, megaloblastic anemia has been associated with the chronic use of Atrium (Phenobarbital).

Other – Nausea and vomiting; headache, osteomalacia.

The following adverse reactions and their incidence were compiled from surveillance of thousands of hospitalized patients who received barbiturates. Because such patients may be less aware of the 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 reaction, 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 are listed below, grouped by organ system and by decreasing order of occurrence:

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

Respiratory System: Hypoventilation, apnea

Cardiovascular System: Bradycardia, hypotension, syncope

Digestive System: Nausea, vomiting, constipation

Other Reported Reactions: Headache, injection site reactions, hypersensitivity reactions (angioedema, skin rashes, exfoliative dermatitis), fever, liver damage, megaloblastic anemia following chronic Atrium (Phenobarbital) use

DRUG ABUSE AND DEPENDENCE

Controlled Substance – Atrium (Phenobarbital) is a Schedule IV drug.

Dependence – Barbiturates may be habit forming. Tolerance, psychological dependence, and physical dependence may occur, especially following prolonged use of high doses of barbiturates. Daily administration in excess of 400 mg of pentobarbital or secobarbital for approximately 90 days is likely to produce some degree of physical dependence. A dosage of 600 to 800 mg taken for at least 35 days is sufficient to produce withdrawal seizures. The average daily dose for the barbiturate addict is usually about 1.5 g. As tolerance to barbiturates develops, the amount needed to maintain the same level of intoxication increases; tolerance to a fatal dosage, however, does not increase more than twofold. As this occurs, the margin between intoxicating dosage and fatal dosage becomes smaller.

Symptoms of acute intoxication with barbiturates include unsteady gait, slurred speech, and sustained nystagmus. Mental signs of chronic intoxication include confusion, poor judgment, irritability, insomnia, and somatic complaints.

Symptoms of barbiturate dependence are similar to those of chronic alcoholism. If an individual appears to be intoxicated with alcohol to a degree that is radically disproportionate to the amount of alcohol in his or her blood, the use of barbiturates should be suspected. The lethal dose of a barbiturate is far less if alcohol is also ingested.

The symptoms of barbiturate withdrawal can be severe and may cause death. Minor withdrawal symptoms may appear 8 to 12 hours after the last dose of a barbiturate. These symptoms usually appear in the following order: anxiety, muscle twitching, tremor of hands and fingers, progressive weakness, dizziness, distortion in visual perception, nausea, vomiting, insomnia, and orthostatic hypotension. Major withdrawal symptoms (convulsions and delirium) may occur within 16 hours and last up to 5 days after abrupt cessation of barbiturates. The intensity of withdrawal symptoms gradually declines over a period of approximately 15 days. Individuals susceptible to barbiturate abuse and dependence include alcoholics and opiate abusers as well as other sedative-hypnotic and amphetamine abusers.

Drug dependence on barbiturates arises from repeated administration of a barbiturate or agent with barbiturate-like effect on a continuous basis, generally in amounts exceeding therapeutic dose levels. The characteristics of drug dependence on barbiturates include: (a) a strong desire or need to continue taking the drug; (b) a tendency to increase the dose; (c) a psychic dependence on the effects of the drug related to subjective and individual appreciation of those effects; and (d) a physical dependence on the effects of the drug, requiring its presence for maintenance of homeostasis and resulting in a definite, characteristic, and self-limited abstinence syndrome when the drug is withdrawn.

Treatment of barbiturate dependence consists of cautious and gradual withdrawal of the drug. Barbiturate-dependent patients can be withdrawn by using a number of different withdrawal regimens. In all cases, withdrawal requires an extended period of time. One method involves substituting a 30-mg dose of Atrium (Phenobarbital) for each 100- to 200-mg dose of barbiturate that the patient has been taking. The total daily amount of Atrium (Phenobarbital) is then administered in 3 or 4 divided doses, not to exceed 600 mg daily. If signs of withdrawal occur on the first day of treatment, a loading dose of 100 to 200 mg of Atrium (Phenobarbital) may be administered IM in addition to the oral dose. After stabilization on Atrium (Phenobarbital), the total daily dose is decreased by 30 mg/day as long as withdrawal is proceeding smoothly. A modification of this regimen involves initiating treatment at the patient’s regular dosage level and decreasing the daily dosage by 10% if tolerated by the patient.

Infants who are physically dependent on barbiturates may be given Atrium (Phenobarbital), 3 to 10 mg/kg/day. After withdrawal symptoms (hyperactivity, disturbed sleep, tremors, and hyperreflexia) are relieved, the dosage of Atrium (Phenobarbital) should be gradually decreased and completely withdrawn over a 2-week period.

OVERDOSAGE

Signs and Symptoms – The onset of symptoms following a toxic oral exposure to Atrium (Phenobarbital) may not occur until several hours following ingestion. 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 to 10 g of ingested barbiturate. The sedated, therapeutic blood levels of Atrium (Phenobarbital) range between 5 to 40 mcg/mL; the usual lethal blood level ranges from 100 to 200 mcg/mL. Barbiturate intoxication may be confused with alcoholism, bromide intoxication, and various neurologic disorders. Potential tolerance must be considered when evaluating significance of dose and plasma concentration.

The manifestations of a long-acting barbiturate in overdose include nystagmus, ataxia, CNS depression, respiratory depression, hypothermia, and hypotension. Other findings may include absent or depressed reflexes and erythematous or hemorrhagic blisters (primarily at pressure points). Following massive exposure to Atrium (Phenobarbital), pulmonary edema, circulatory collapse with loss of peripheral vascular tone, cardiac 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 should not 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 – To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. Telephone numbers of certified poison control centers are listed in the Physicians’ Desk Reference (PDR). In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.

Protect the patient’s airway and support ventilation and perfusion. Meticulously monitor and maintain, within acceptable limits, the patient’s vital signs, blood gases, serum electrolytes, etc. Absorption of drugs from the gastrointestinal tract may be decreased by giving activated charcoal, which, in many cases, is more effective than emesis or lavage; consider charcoal instead of or in addition to gastric emptying. Repeated doses of charcoal over time may hasten elimination of some drugs that have been absorbed. Safeguard the patient’s airway when employing gastric emptying or charcoal.

Alkalinization of urine hastens Atrium (Phenobarbital) excretion, but dialysis and hemoperfusion are more effective and cause less troublesome alterations in electrolyte equilibrium. If the patient has chronically abused sedatives, withdrawal reactions may be manifest following acute overdose.

DOSAGE AND ADMINISTRATION

The dose of Atrium (Phenobarbital) must be individualized with full knowledge of its particular characteristics. Factors of consideration are the patient’s age, weight, and condition.

Sedation:

For sedation, the drug may be administered in single dose of 30 to 120 mg repeated at intervals: frequency will be determined by the patient’s response. It is generally considered that no more than 400 mg of Atrium (Phenobarbital) should be administered during a 24-hour period.

Adults:

Daytime Sedation: 30 to 120 mg daily in 2 to 3 divided doses.

Oral Hypnotic: 100 to 200 mg.

Anticonvulsant Use – Clinical laboratory reference values should be used to determine the therapeutic anticonvulsant level of Atrium (Phenobarbital) in the serum. To achieve the blood levels considered therapeutic in pediatric patients, higher per-kilogram dosages are generally necessary for Atrium (Phenobarbital) and most other anticonvulsants. In children and infants, Atrium (Phenobarbital) at a loading dose of 15 to 20 mg/kg produces blood levels of about 20 mcg/mL shortly after administration.

Atrium (Phenobarbital) has been used in the treatment and prophylaxis of febrile seizures. However, it has not been established that prevention of febrile seizures influences the subsequent development of epilepsy.

Adults: 60 to 200 mg/day.

Pediatric Patients: 3 to 6 mg/kg/day.

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.

HOW SUPPLIED

Atrium (Phenobarbital) Tablets, USP 16.2 mg are white, round, biconvex, scored tablets, debossed “5011” and “V” on one side and plain on the reverse side, and supplied as follows:

• Bottles of 100 NDC 0603-5165-21
• Bottles of 1000 NDC 0603-5165-32

Atrium (Phenobarbital) Tablets, USP 32.4 mg are white, round, biconvex, scored tablets, debossed “5012” and “V” on one side and plain on the reverse side, and supplied as follows:

• Bottles of 30 NDC 0603-5166-16
• Bottles of 60 NDC 0603-5166-20
• Bottles of 90 NDC 0603-5166-02
• Bottles of 100 NDC 0603-5166-21
• Bottles of 120 NDC 0603-5166-22
• Bottles of 1000 NDC 0603-5166-32

Atrium (Phenobarbital) Tablets, USP 64.8 mg are white, round, biconvex, scored tablets, debossed “5013” and “V” on one side and plain on the reverse side, and supplied as follows:

• Bottles of 100 NDC 0603-5167-21
• Bottles of 1000 NDC 0603-5167-32

Atrium (Phenobarbital) Tablets, USP 97.2 mg are white, round, biconvex, scored tablets, debossed “5014” and “V” on one side and plain on the reverse side, and supplied as follows:

• Bottles of 100 NDC 0603-5168-21
• Bottles of 1000 NDC 0603-5168-32

Manufactured for:

QUALITEST PHARMACEUTICALS

Huntsville, AL 35811

8180067

Rev 7/14

R4