Phrenilin

PHRENILIN- butalbital and acetaminophen tablet
PHRENILIN FORTE- butalbital and acetaminophen capsule
Valeant Pharmaceuticals International

Rx Only

WARNING: Hepatotoxicity

Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 milligrams per day, and often involve more than one acetaminophen containing product.

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:

Chemical Structure

C11 H16 N2 O3 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:

Chemical Structure

C8 H9 NO2 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.

Phrenilin 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 habit-forming 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.

Hepatotoxicity

Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 milligrams per day, and often involve more than one acetaminophen-containing product. The excessive intake of acetaminophen may be intentional to cause self-harm or unintentional as patients attempt to obtain more pain relief or unknowingly take other acetaminophen-containing products.

The risk of acute liver failure is higher in individuals with underlying liver disease and in individuals who ingest alcohol while taking acetaminophen.

Instruct patients to look for acetaminophen or APAP on package labels and not to use more than one product that contains acetaminophen. Instruct patients to seek medical attention immediately upon ingestion of more than 4000 milligrams of acetaminophen per day, even if they feel well.

Hypersensitivity/anaphylaxis

There have been post-marketing reports of hypersensitivity and anaphylaxis associated with use of acetaminophen. Clinical signs included swelling of the face, mouth, and throat, respiratory distress, urticaria, rash, pruritus, and vomiting. There were infrequent reports of life-threatening anaphylaxis requiring emergency medical attention. Instruct patients to discontinue PHRENILIN® tablets or PHRENILIN® FORTE capsules immediately and seek medical care if they experience these symptoms. Do not prescribe PHRENILIN® tablets or PHRENILIN® FORTE capsules for patients with acetaminophen allergy.

PRECAUTIONS

General:

PHRENILIN® tablets and PHRENILIN® FORTE capsules 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/CAREGIVERS

  • Do not take PHRENILIN® tablets or PHRENILIN® FORTE capsules if you are allergic to any of the ingredients.
  • If you develop signs of allergy such as a rash or difficulty breathing stop taking PHRENILIN® or PHRENILIN® FORTE and contact your healthcare provider immediately.
  • Do not take more than 4000 milligrams of acetaminophen per day. Call your doctor if you took more than the recommended dose.

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.

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