Phenobarbital is a barbituric acid derivative for oral administration and occurs as a white, odorless, slightly bitter powder that is soluble in chloroform, freely soluble in alcohol or ether, and slightly soluble in water. Its saturated solution has a pH of about 5.6. Chemically, it is 5-ethyl-5-phenylbarbituric acid with the molecular formula C12H12N2O3 (232.24). The structural formula is as follows:

Each Phenobarbital Tablet, USP contains 15 mg, 30 mg, 60 mg or 100 mg of phenobarbital, USP.

Inactive Ingredients are as follows:

Anhydrous Lactose, Colloidal Silicon Dioxide, Corn Starch, Docusate Sodium with Sodium Benzoate, Lactose Monohydrate, Magnesium Stearate, Microcrystalline Cellulose, and Sodium Starch Glycolate.

Phenobarbital, a long-acting barbiturate, is a central nervous system depressant. In ordinary doses, the drug acts as a sedative and anticonvulsant. Its onset of action occurs within 30 minutes, and the duration of action ranges from 5 to 6 hours. It is detoxified in the liver.

Phenobarbital Tablets, USP are indicated for use as a sedative or anticonvulsant.

Phenobarbital is contraindicated in patients who are hypersensitive to barbiturates. In such patients, severe hepatic damage can occur from ordinary doses and is usually associated with dermatitis and involvement of parenchymatous organs. A personal or familial history of acute intermittent porphyria represents one of the few absolute contraindications to the use of barbiturates. Phenobarbital is also contraindicated in patients with marked impairment of liver function, or respiratory disease in which dyspnea or obstruction is evident. It should not be administered to persons with known previous addiction to the sedative/hypnotic group, since ordinary doses may be ineffectual and may contribute to further addiction.

In small doses, the barbiturates may increase the reaction to painful stimuli. Taken by themselves, the barbiturates cannot be relied upon to relieve pain or even to produce sedation or sleep in the presence of severe pain.

The following adverse reactions have been reported:

Controlled Substance: Phenobarbital is a Schedule IV drug.

The signs and symptoms of barbiturate poisoning are referable especially to the central nervous system and the cardiovascular system. Moderate intoxication resembles alcoholic inebriation. In severe intoxication, the patient is comatose, the level of reflex activity conforming in a general way to the intensity of the central depression. The deep reflexes may persist for some time despite coexistent coma. The Babinski sign is often positive. The EEG may be of the “burst-suppression” type, with brief periods of electrical silence. The pupils may be constricted and react to light, but late in the course of barbiturate poisoning they may show hypoxic paralytic dilatation. Respiration is affected early. Breathing may be either slow or rapid and shallow; Cheyne-Stokes rhythm may be present. Respiratory minute volume is diminished, and hypoxia and respiratory acidosis may develop. The blood pressure falls, owing partly to depression of medullary vasomotor centers; partly to a direct action of the drug on the myocardium, sympathetic ganglia, and vascular smooth muscle; partly to hypoxia.

The patient thus develops a typical shock syndrome, with a weak and rapid pulse, cold and clammy skin, and a rise in the hematocrit. Respiratory complications (atelectasis, pulmonary edema, and bronchopneumonia) and renal failure are much dreaded and not infrequent concomitant of severe barbiturate poisoning. There is usually hypothermia, sometimes with temperatures as low as 32°C.

Oral Sedative Dose

Adults: 30 to 120 mg daily in 2 or 3 divided doses.

Children: 6 mg/kg of body weight daily in 3 divided doses.

Oral Hypnotic Dose

Adults: 100 to 320 mg.

Oral Anticonvulsant Dose,

Adults: 50 to 100 mg 2 or 3 times daily.

Children: 15 to 50 mg 2 or 3 times daily.

Phenobarbital Tablets USP, 15 mg

White, Round Tablet; Debossed “WW 445” on one side and plain on the other side.              

              NDC 0143-1495-01: Bottle of 100 tablets 
              NDC 0143-1495-05: Bottle of 500 tablets  

Phenobarbital Tablets USP, 30 mg

White, Round, Scored Tablet; Debossed “WW 450” on one side and Scored on the other side.

             NDC 0143-1500-01: Bottle of 100 tablets   
             NDC 0143-1500-05: Bottle of 500 tablets  

Phenobarbital Tablets USP, 60 mg

White, Round Tablet; Debossed “WW 455” on one side and plain on the other side.

             NDC 0143-1455-01: Bottle of 100 tablets 
             NDC 0143-1455-05: Bottle of 500 tablets

Phenobarbital Tablets USP, 100 mg

White, Round, Scored Tablet; Debossed “WW 458” on one side and Scored on the other side.

             NDC 0143-1458-01: Bottle of 100 tablets  
             NDC 0143-1458-05: Bottle of 500 tablets

Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature]. Protect from light and moisture.

Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.

Distributed by:
Hikma Pharmaceuticals USA Inc.
Berkeley Heights,  NJ 07922

C50000803/02      Revised August 2022

NDC 0143-1495-01
Phenobarbital Tablets USP 
15 mg
100 Tablets
Rx Only

NDC 0143-1500-01
Phenobarbital Tablets USP 
30 mg
100 Tablets
Rx Only

NDC 0143-1455-01
Phenobarbital Tablets USP 
60 mg
100 Tablets
Rx Only

NDC 0143-1458-01
Phenobarbital Tablets USP 
100 mg
100 Tablets
Rx Only