Inform Your Physician Before Taking This Drug If

• you are allergic or overly sensitive to any barbiturate drug (see Drug Class, Section Four).

• you are pregnant or planning pregnancy.

• you have a history of alcohol or drug abuse.

• you are taking any drugs with sedative effects.

• you have any type of seizure disorder.

• you have myasthenia gravis.

• you have impaired liver, kidney or thyroid gland function.

• you plan to have surgery under general anesthesia in the near future.

Possible Side-Effects (natural, expected and unavoidable drug actions) Drowsiness, impaired concentration, mental and physical sluggishness.

Possible Adverse Effects (unusual, unexpected and infrequent reactions) If any of the following develop, consult your physician promptly for guidance.

Mild Adverse Effects Allergic Reactions: Skin rashes, hives, localized swellings of face, drug

fever (see Glossary).

Dizziness, unsteadiness, impaired vision, double vision. Nausea, vomiting, diarrhea. Shoulder-hand syndrome: pain and stiffness in the shoulder, pain and swelling in the hand.

Serious AdverseEffects

Allergic Reactions: Drug-induced hepatitis with jaundice (see Glossary). Idiosyncratic Reactions: Paradoxical excitement and delirium (instead of

sedation).

Mental depression, abnormal involuntary movements. Blood cell disorders: deficiencies of all blood cell types causing fatigue,

weakness, fever, sore throat, abnormal bleeding or bruising.

Possible Effects on Sexual Function

Decreased libido and/or impotence (16%).

Decreased effectiveness of oral contraceptives taken concurrently (71%).

Adverse Effects That May Mimic Natural Diseases or Disorders

Liver reactions may suggest viral hepatitis.

Natural Diseases or Disorders That May Be Activated by This Drug

Acute intermittent and/or cutaneous porphyria, systemic lupus ery­thematosus.

Possible Effects on Laboratory Tests

Complete blood cell counts: decreased red cells, hemoglobin, white cells and platelets.

Blood lupus erythematosus (LE) cells: positive.

Prothrombin time: decreased (when taken concurrently with warfarin).

Blood calcium level: decreased (with long-term use).

Blood thyroxine (T⁴) level: decreased.

Liver function tests: increased liver enzymes (ALT/GPT, AST/GOT and alkaline phosphatase), increased bilirubin.

Urine sugar tests: no effect with TesTape; false low results with Clinistix and Diastix.

Urine screening tests for drug abuse: may be positive. (Test results depend upon amount of drug taken and testing method used.)

CAUTION

1. Anticonvulsant drug therapy must be carefully individualized. Accu­rate diagnosis and classification of the seizure pattern are essential to the correct selection of the most appropriate drug for seizure control.

2. Emotional stress or physical trauma (including surgery) may require increased anticonvulsant dosage to control seizures.

3. Prolonged-action dosage forms of this drug are not appropriate for the treatment of seizures and should not be used.

Precautions for Use

By Infants and Children: This drug should not be given to the hyperkinetic child. Observe for possible paradoxical stimulation and hyperactivity; this can occur in 10% to 40% of children. Changes associated with puberty characteristically slow the metabolism of this drug and permit its gradual accumulation. Blood levels of this drug in young adoles­cents should be monitored every 3 months to detect rising concentra­tions and early toxicity. Adjust dosage as necessary.

By Those over 60 Years of Age: It is advisable to avoid all barbiturates in the elderly. If use of this drug is attempted, start with small doses until tolerance has been determined. Observe for confusion, delirium, agita­tion and excitement. Do not use this drug concurrently with other drugs for mental disorders. This drug is conducive to the development of hypothermia (see Glossary).

Advisability of Use During Pregnancy

Pregnancy Category: D (tentative). See Pregnancy Code inside back cover.

Animal studies: Conflicting reports of cleft palate and skeletal defects in mouse, rat and rabbit studies.

Human studies: Information from studies of pregnant women indicates no increase in birth defects in 8037 exposures to this drug. However, it is reported that barbiturates can cause fetal damage when taken during pregnancy.

Avoid use of drug during entire pregnancy if possible. If it is clearly needed to control seizures, the mother should receive vitamin К prior to delivery and the infant should receive it at birth.

Advisability of Use if Breast-Feeding

Presence of this drug in breast milk: Yes, in small amounts. Monitor nursing infant closely and discontinue drug or nursing if adverse effects develop.

Habit-Forming Potential: Psychological and physical dependence can occur with prolonged use of excessive doses—300 to 700 mg/day for 1 to 2 months. Dependence is not likely to occur with usual sedative or anticonvulsant doses.

Effects of Overdosage: Behavior similar to alcoholic intoxication: confusion, slurred speech, physical incoordination, staggering gait, drowsi­ness, stupor progressing to coma.

Possible Effects of Long-Term Use: Psychological and/or physical dependence; syndrome of chronic intoxication: headache, depression, im­paired vision, dizziness, slurred speech, incoordination.Megaloblastic anemia due to folic acid deficiency. Rickets or osteomalacia due to deficiencies of vitamin D and calcium.

Suggested Periodic Examinations While Taking This Drug (at physician's

discretion)

Complete blood cell counts, liver function tests.

During long-term use: blood levels of folic acid, vitamin B-12, calcium and phosphorus; skeletal X-ray studies for demineralization of bone.

While Taking This Drug, Observe the Following

Foods: No restrictions. Eat liberally of foods rich in folic acid: fortified breakfast cereals, liver, legumes, green leafy vegetables.

Beverages: No restrictions. May be taken with milk or fruit juices.

Alcohol: Avoid completely. Alcohol can increase greatly the sedative and depressant actions of this drug on brain functions.

Tobacco Smoking: May enhance the sedative effects of this drug and in­crease drowsiness.

Marijuana Smoking: Increased drowsiness, unsteadiness; significantly im­paired mental and physical performance.

Other Drugs Phenobarbital may increase the effects of

• all other drugs with sedative effects, and cause excessive sedation. Phenobarbital may decrease the effects of

• anticoagulants (Coumadin, etc.), and require dosage adjustments.

• certain beta blockers (Inderal, Lopressor), and reduce their effective­ ness.

• cortisonelike drugs.

• doxycycline (Vibramycin), and reduce its effectiveness.

• griseofulvin (Fulvicin, etc.), and reduce its effectiveness.

• oral contraceptives, and reduce their effectiveness in preventing preg­ nancy.

• quinidine (Quinaglute, etc.), and reduce its effectiveness.

• theophyllines (Aminophyllin, Theo-Dur, etc.), and reduce their an­ tiasthmatic effectiveness.

Phenobarbital taken concurrently with

• phenytoin (Dilantin) may alter phenytoin blood levels: a high pheno­ barbital level will increase the phenytoin level; a low phenobarbital level will decrease the phenytoin level. Periodic determination of blood levels of both drugs is advised.

The following drugs may increase the effects of phenobarbital

• valproic acid (Depakene).

Driving, Hazardous Activities: This drug may cause drowsiness and may

impair mental alertness, judgment, physical coordination and reaction

time. Restrict activities as necessary. Aviation Note: The use of this drug is a disqualification for piloting.

Consult a designated Aviation Medical Examiner. Exposure to Sun: Use caution until sensitivity has been determined. This

drug may cause photosensitivity.

Exposure to Cold: Observe the elderly for possible hypothermia while taking this drug.

Discontinuation: If used as an anticonvulsant, this drug must not be discontinued abruptly. Sudden withdrawal can precipitate status epilepticus (repetitive seizures). Gradual reduction in dosage should be made over a period of 3 months. Total drug withdrawal may be attempted after a period of 3 to 5 years without a seizure. However, seizures are likely to recur in 40% of adults and in 20% to 30% of children.

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