RxNorm Names
Review RxNorm Normal Forms
phrenilin (butalbital and acetaminophen) tablet
phrenilin forte (butalbital and acetaminophen) capsule
[Valeant Pharmaceuticals North America]
Rx Only
DESCRIPTION
PHRENILIN®: Each PHRENILIN® tablet for oral administration, contains Butalbital, USP 50 mg, Acetaminophen, USP 325 mg.
In addition each PHRENILIN® tablet contains the following inactive ingredients: alginic acid, corn starch, D&C Red No. 27 - Aluminum Lake, FD&C Blue No. 1 - Aluminum Lake, gelatin, magnesium stearate, microcrystalline cellulose and pregelatinized starch.
PHRENILIN® FORTE: Each PHRENILIN® FORTE capsule for oral administration, contains Butalbital, USP 50 mg, Acetaminophen, USP 650 mg.
In addition each PHRENILIN® FORTE capsule may also contain the following inactive ingredients: benzyl alcohol, butylparaben, D&C Red No. 28, D&C Red No. 33, edetate calcium disodium, FD&C Blue No. 1, FD&C Red No. 40, gelatin, methylparaben, propylparaben, silicon dioxide, sodium lauryl sulfate, sodium propionate and titanium dioxide.
Butalbital (5-allyl-5-isobutylbarbituric acid), a slightly bitter, white, odorless, crystalline powder, is a short to intermediate-acting barbiturate. It has the following structural formula:
C11H16N2O3 M.W. = 224.26
Acetaminophen (4'-hydroxyacetanilide), a slightly bitter, white, odorless, crystalline powder, is a non-opiate, non-salicylate analgesic and antipyretic. It has the following structural formula:
C8H9NO2 M.W. = 151.16
CLINICAL PHARMACOLOGY
This combination drug product is intended as a treatment for tension headache.
It consists of a fixed combination of butalbital and acetaminophen. The role each component plays in the relief of the complex of symptoms known as tension headache is incompletely understood.
Pharmacokinetics: The behavior of the individual components is described below.
Butalbital: Butalbital is well absorbed from the gastrointestinal tract and is expected to distribute to most tissues in the body. Barbiturates in general may appear in breast milk and readily cross the placental barrier. They are bound to plasma and tissue proteins to a varying degree and binding increases directly as a function of lipid solubility.
Elimination of butalbital is primarily via the kidney (59% to 88% of the dose) as unchanged drug or metabolites. The plasma half-life is about 35 hours. Urinary excretion products include parent drug (about 3.6% of the dose), 5-isobutyl-5-(2,3-dihydroxy-propyl) barbituric acid (about 24% of the dose), 5-allyl-5 (3-hydroxy-2-methyl-1-propyl) barbituric acid (about 4.8% of the dose), products with the barbituric acid ring hydrolyzed with excretion of urea (about 14% of the dose), as well as unidentified materials. Of the material excreted in the urine, 32% is conjugated.
See OVERDOSAGE for toxicity information.
Acetaminophen: Acetaminophen is rapidly absorbed from the gastrointestinal tract and is distributed throughout most body tissues. The plasma half-life is 1.25 to 3 hours, but may be increased by liver damage and following overdosage. Elimination of acetaminophen is principally by liver metabolism (conjugation) and subsequent renal excretion of metabolites. Approximately 85% of an oral dose appears in the urine within 24 hours of administration, most as the glucuronide conjugate, with small amounts of other conjugates and unchanged drug.
See OVERDOSAGE for toxicity information.
INDICATIONS AND USAGE
PHRENILIN® tablets and PHRENILIN® FORTE capsules are indicated for the relief of the symptom complex of tension (or muscle contraction) headache.
Evidence supporting the efficacy and safety of this combination product in the treatment of multiple recurrent headaches is unavailable. Caution in this regard is required because butalbital is habitforming and potentially abusable.
CONTRAINDICATIONS
This product is contraindicated under the following conditions:
-
Hypersensitivity or intolerance to any component of this product.
-
Patients with porphyria.
WARNINGS
Butalbital is habit-forming and potentially abusable. Consequently, the extended use of this product is not recommended.
PRECAUTIONS
General:
PHRENILIN® tablets and PHRENILIN® FORTE capsules (Butalbital and Acetaminophen) should be prescribed with caution in certain special-risk patients, such as the elderly or debilitated, and those with severe impairment of renal or hepatic function, or acute abdominal conditions.
Information for Patients:
This product may impair mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving a car or operating machinery. Such tasks should be avoided while taking this product.
Alcohol and other CNS depressants may produce an additive CNS depression, when taken with this combination product, and should be avoided.
Butalbital may be habit-forming. Patients should take the drug only for as long as it is prescribed, in the amounts prescribed, and no more frequently than prescribed.
Laboratory Tests:
In patients with severe hepatic or renal disease, effects of therapy should be monitored with serial liver and/or renal function tests.
Drug Interactions:
The CNS effects of butalbital may be enhanced by monoamine oxidase (MAO) inhibitors.
Butalbital and acetaminophen may enhance the effects of: other narcotic analgesics, alcohol, general anesthetics, tranquilizers such as chlordiazepoxide, sedative-hypnotics, or other CNS depressants, causing increased CNS depression.
Drug/Laboratory Test Interactions:
Acetaminophen may produce false-positive test results for urinary 5-hydroxyindoleacetic acid.
Carcinogenesis, Mutagenesis, Impairment of Fertility:
No adequate studies have been conducted in animals to determine whether acetaminophen or butalbital have a potential for carcinogenesis, mutagenesis or impairment of fertility.
Pregnancy:
Teratogenic Effects: Pregnancy Category C: Animal reproduction studies have not been conducted with this combination product. It is also not known whether butalbital and acetaminophen can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. These products should be given to a pregnant woman only when clearly needed.
Nonteratogenic Effects: Withdrawal seizures were reported in a two-day-old male infant whose mother had taken a butalbital-containing drug during the last two months of pregnancy. Butalbital was found in the infant's serum. The infant was given phenobarbital 5 mg/kg, which was tapered without further seizure or other withdrawal symptoms.
Nursing Mothers:
Barbiturates and acetaminophen are excreted in breast milk in small amounts, but the significance of their effects on nursing infants is not known. Because of potential for serious adverse reactions in nursing infants from butalbital and acetaminophen, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatric Use:
Safety and effectiveness in children below the age of 12 have not been established.
ADVERSE REACTIONS
Frequently Observed: The most frequently reported adverse reactions are drowsiness, lightheadedness, dizziness, sedation, shortness of breath, nausea, vomiting, abdominal pain, and intoxicated feeling.
Infrequently Observed: All adverse events tabulated below are classified as infrequent.
Central Nervous: headache, shaky feeling, tingling, agitation, fainting, fatigue, heavy eyelids, high energy, hot spells, numbness, sluggishness, seizure. Mental confusion, excitement or depression can also occur due to intolerance, particularly in elderly or debilitated patients, or due to overdosage of butalbital.
Autonomic Nervous: dry mouth, hyperhidrosis.
Gastrointestinal: difficulty swallowing, heartburn, flatulence, constipation.
Cardiovascular: tachycardia.
Musculoskeletal: leg pain, muscle fatigue.
Genitourinary: diuresis.
Miscellaneous: pruritus, fever, earache, nasal congestion, tinnitus, euphoria, allergic reactions.
Several cases of dermatological reactions, including toxic epidermal necrolysis and erythema multiforme, have been reported.
The following adverse drug events may be borne in mind as potential effects of the components of this product. Potential effects of high dosage are listed in the OVERDOSAGE section.
Acetaminophen: allergic reactions, rash, thrombocytopenia, agranulocytosis.
DRUG ABUSE AND DEPENDENCE
Abuse and Dependence: Butalbital: Barbiturates may be habit-forming: Tolerance, psychological dependence, and physical dependence may occur especially following prolonged use of high doses of barbiturates. The average daily dose for the barbiturate addict is usually about 1500 mg. 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 two-fold. As this occurs, the margin between an intoxication dosage and fatal dosage becomes smaller. The lethal dose of a barbiturate is far less if alcohol is also ingested. Major withdrawal symptoms (convulsions and delirium) may occur within 16 hours and last up to 5 days after abrupt cessation of these drugs. Intensity of withdrawal symptoms gradually declines over a period of approximately 15 days. 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. One method involves initiating treatment at the patient's regular dosage level and gradually decreasing the daily dosage as tolerated by the patient.
OVERDOSAGE
Following an acute overdosage of butalbital and acetaminophen, toxicity may result from the barbiturate or the acetaminophen.
Signs and Symptoms: Toxicity from barbiturate poisoning includes drowsiness, confusion, and coma; respiratory depression; hypotension; and hypovolemic shock.
In acetaminophen overdosage: dose-dependent, potentially fatal hepatic necrosis is the most serious adverse effect. Renal tubular necroses, hypoglycemic coma and thrombocytopenia may also occur. Early symptoms following a potentially hepatotoxic overdose may include: nausea, vomiting, diaphoresis and general malaise. Clinical and laboratory evidence of hepatic toxicity may not be apparent until 48 to 72 hours post-ingestion. In adults hepatic toxicity has rarely been reported with acute overdoses of less than 10 grams, or fatalities with less than 15 grams.
Treatment: A single or multiple overdose with these combination products is a potentially lethal polydrug overdose, and consultation with a regional poison control center is recommended.
Immediate treatment includes support of cardiorespiratory function and measures to reduce drug absorption. Vomiting should be induced mechanically, or with syrup of ipecac, if the patient is alert (adequate pharyngeal and laryngeal reflexes). Oral activated charcoal (1 g/kg) should follow gastric emptying. The first dose should be accompanied by an appropriate cathartic. If repeated doses are used, the cathartic might be included with alternate doses as required. Hypotension is usually hypovolemic and should respond to fluids. Pressors should be avoided. A cuffed endotracheal tube should be inserted before gastric lavage of the unconscious patient and, when necessary, to provide assisted respiration. 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, especially phenobarbital.
Meticulous attention should be given to maintaining adequate pulmonary ventilation. In severe cases of intoxication, peritoneal dialysis, or preferably hemodialysis may be considered. If hypoprothrombinemia occurs due to acetaminophen overdose, vitamin K should be administered intravenously.
If the dose of acetaminophen may have exceeded 140 mg/kg, acetylcysteine should be administered as early as possible. Serum acetaminophen levels should be obtained, since levels four or more hours following ingestion help predict acetaminophen toxicity. Do not await acetaminophen assay results before initiating treatment. Hepatic enzymes should be obtained initially, and repeated at 24-hour intervals.
Methemoglobinemia over 30% should be treated with methylene blue by slow intravenous administration.
Toxic Doses (for adults):
Phrenilin® tablets (Butalbital 50 mg and acetaminophen 325 mg tablets)
Butalbital:
toxic dose 1 g (20 tablets)
Acetaminophen:
toxic dose 10 g (30 tablets)
PHRENILIN® FORTE capsules (Butalbital 50 mg and acetaminophen 650 mg capsules)
Butalbital:
toxic dose 1 g (20 capsules)
Acetaminophen:
toxic dose 10 g (15 capsules)
DOSAGE AND ADMINISTRATION
PHRENILIN®: One or two tablets every four hours. Total daily dosage should not exceed 6 tablets.
PHRENILIN® FORTE: One capsule every four hours. Total daily dosage should not exceed 6 capsules.
Extended and repeated use of these products is not recommended because of the potential for physical dependence.
HOW SUPPLIED
PHRENILIN®: Pale violet scored tablets with the letter V on one side and 0842 on the other, in bottles of 100 (NDC 0187-0842-01). Each tablet contains butalbital, USP 50 mg and acetaminophen, USP 325 mg.
PHRENILIN® FORTE: Amethyst, opaque capsules imprinted with Valeant and PF0844, in bottles of 100 (NDC 0187-0844-01) and 500 (NDC 0187-0844-02). Each capsule contains butalbital, USP 50 mg and acetaminophen, USP 650 mg.
Store PHRENILIN® and PHRENILIN® FORTE (Butalbital and Acetaminophen) at 25°C (77°F); excursions permitted to 15°C-30°C (59°F-86°F). Dispense in a tight container as defined in the USP.
Distributed by:
Valeant Pharmaceuticals North America
One Enterprise
Aliso Viejo, CA 92656 USA
Manufactured by:
Mallinckrodt Inc.
Hobart, NY 13788
Insert printed with food grade ink.
MG #21838
Rev. 03/07
Part No. L2PP06
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Revised: 08/2008Valeant Pharmaceuticals North America
