Phenobarbital Sodium

DOSAGE AND ADMINISTRATION Dosages of barbiturates must be individualized with full knowledge of their particular characteristics and recommended rates of administration. Factors to consider are the patient's age, weight and condition. Suggested doses of phenobarbital sodium for specific indications follow: Pediatric Dosage Recommended by the American Academy of Pediatrics (intended as a guide) Preoperative Sedation: 1 to 3 mg/kg intramuscular or intravenous Anticonvulsion: 4 to 6 mg/kg/day for 7 to 10 days to blood level of 10 to 15 mcg/mL or 10 to 15 mg/kg/day intramuscular or intravenous Status Epilepticus: 15 to 20 mg/kg over 10 to 15 minutes intravenous Adult Dosage (intended as a guide) Daytime Sedation: 30 to 120 mg daily in 2 to 3 divided doses intramuscular or intravenous Bedtime Hypnosis: 100 to 320 mg intramuscular or intravenous Preoperative Sedation: intramuscular only - 100 to 200 mg 60 to 90 minutes before surgery Acute Convulsions: 20 to 320 mg intramuscular or intravenous, repeated in 6 hours as necessary Parenteral routes should be used only when oral administration is impossible or impractical. Intramuscular injection of the sodium salts of barbiturates should be made deeply into a large muscle and a volume of 5 mL should not be exceeded at any one site because of possible tissue irritation. Injection into or near peripheral nerves may result in permanent neurological deficit. After intramuscular injection of a hypnotic dose, the patient's vital signs should be monitored. Subcutaneous administration is not recommended (see CONTRAINDICATIONS ). Intravenous Administration Intravenous injection is restricted to conditions in which other routes are not feasible, either because the patient is unconscious (as in cerebral hemorrhage, eclampsia or status epilepticus), or because the patient resists (as in delirium) or because prompt action is imperative. Slow intravenous injection is essential, and patients should be carefully observed during administration. This requires that blood pressure, respiration and cardiac function be maintained, vital signs be recorded and equipment for resuscitation and artificial ventilation be available. The rate of intravenous injection for adults should not exceed 60 mg/min. for phenobarbital sodium. When given intravenously, do not use small veins, such as those on the dorsum of the hand or wrist. Preference should be given to a larger vein to minimize the risk of irritation with the possibility of resultant thrombosis. Avoid administration into varicose veins because circulation there is retarded. Inadvertent injection into or adjacent to an artery has resulted in gangrene requiring amputation of an extremity or a portion thereof. Careful technique, including aspiration, is necessary to avoid inadvertent intraarterial injection. (See below.) Treatment of Adverse Effects Due to Inadvertent Error in Administration Extravasation into subcutaneous tissues causes tissue irritation. This may vary from slight tenderness and redness to necrosis. Recommended treatment includes the application of moist heat and the injection of 0.5% procaine solution into the affected area. Intraarterial injection of any barbiturate must be avoided. The accidental intraarterial injection of a small amount of the solution may cause spasm and severe pain along the course of the artery. The injection should be terminated if the patient complains of pain or if other indications of accidental intraarterial injection occur, such as a white hand with cyanosed skin or patches of discolored skin and delayed onset of hypnosis. The consequences of intraarterial injection of phenobarbital can vary from transient pain to gangrene. It is not possible to formulate strict rules for management of such accidents. The following procedures have been suggested: 1) release of the tourniquet or restrictive garments to permit dilution of injected drug, 2) relief of arterial spasm by injecting 10 mL of a 1% procaine solution into the artery and, if considered necessary, brachial plexus block, 3) prevention of thrombosis by early anticoagulant therapy and 4) supportive treatment. Anticonvulsant Use A therapeutic anticonvulsant level of phenobarbital in the serum is 10 to 25 μg/mL. To achieve the blood levels considered therapeutic in children, higher per-kilogram dosages are generally necessary for phenobarbital and most other anticonvulsants. In children and infants, phenobarbital at loading doses of 15 to 20 mg/kg produces blood levels of about 20 μg/mL shortly after administration. In status epilepticus, it is imperative to achieve therapeutic blood levels of a barbiturate (or other anticonvulsants) as rapidly as possible. When administered intravenously, phenobarbital sodium may require 15 minutes or more to attain peak concentrations in the brain. If phenobarbital sodium is injected continuously until the convulsions stop, the brain concentration will continue to rise and can eventually exceed that required to control the seizures. Because a barbiturate-induced depression may occur along with a postictal depression once the seizures are controlled, it is important, therefore, to use the minimal amount required and to wait for the anticonvulsant effect to develop before administering a second dose. 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. 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. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

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INDICATIONS AND USAGE Parenteral Sedative.