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-dihydroxypropyl) 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.

The in vitro plasma protein binding of butalbital is 45% over the concentration range of 0.5-20 mcg/mL. This falls within the range of plasma protein binding (20%-45%) reported with other barbiturates such as phenobarbital, pentobarbital, and secobarbital sodium. The plasma-to-blood concentration ratio was almost unity, indicating that there is no preferential distribution of butalbital into either plasma or blood cells.

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.

Caffeine

Like most xanthines, caffeine is rapidly absorbed and distributed in all body tissues and fluids, including the CNS, fetal tissues, and breast milk.

Caffeine is cleared through metabolism and excretion in the urine. The plasma half-life is about 3 hours. Hepatic biotransformation prior to excretion results in about equal amounts of 1-methylxanthine and 1-methyluric acid. Of the 70% of the dose that is recovered in the urine, only 3% is unchanged drug.

What is the most important information I should know about Fioricet?

• • Butalbital, one of the drugs found in Fioricet, is habit-forming and has potential for abuse. Extended use is not recommended.Fioricet can affect your ability to drive a car or operate machinery. Do not drive a car or operate machinery while taking Fioricet until you know how this drug affects you.Avoid alcohol and other drugs that affect your central nervous system (brain and spinal cord) because they can further affect your ability to concentrate.
  • Who should not take Fioricet?Do not take Fioricet if you are allergic to butalbital, acetaminophen, or caffeine.Do not take Fioricet if you have an inherited disorder that affects the liver or bone marrow (porphyria).

What should I tell my doctor before I take the first dose of Fioricet?

• • Tell your doctor about all prescription, over-the-counter, and herbal medications you are taking before beginning treatment with Fioricet. Also, talk to your doctor about your complete medical history, especially if you have porphyria, kidney or liver disease, a history of prior substance abuse, if you drink alcohol, are pregnant, plan to become pregnant, or are breastfeeding.

What is the usual dosage?

• The information below is based on the dosage guidelines your doctor uses. Depending on your condition and medical history, your doctor may prescribe a different regimen. Do not change the dosage or stop taking your medication without your doctor’s approval.Adults: The usual dose of Fioricet is 1 or 2 tablets taken every 4 hours as needed. One tablet contains 50 milligrams (mg) of butalbital, 325 mg of acetaminophen, and 40 mg of caffeine. Do not take more than 6 tablets per day.Elderly: Your doctor may prescribe a lower dose than the usual recommended dose to suit your needs.Children: Fioricet is not recommended in children <12 years old.

How should I take Fioricet?

• Take Fioricet exactly as prescribed. Do not increase the amount you take without your doctor’s approval. Do not take more than 6 tablets per day.

What should I avoid while taking Fioricet?

• • • Fioricet can cause drowsiness or dizziness. Avoid driving, operating machinery, or performing other hazardous activities while taking Fioricet.Avoid taking Fioricet with medications that affect your concentration, such as other narcotic pain relievers, general anesthetics, sleeping pills, anti-allergy medications, sedative-hypnotics, and tranquilizers (such as chlordiazepoxide). These may cause further drowsiness.Do not drink alcohol while taking Fioricet. Doing so may result in increased drowsiness and dizziness.Avoid taking other medications that contain acetaminophen, such as Tylenol. Avoid taking too much caffeine.

What are possible food and drug interactions associated with Fioricet?

• • If Fioricet is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining Fioricet with any of the following: alcohol, general anesthetics, antidepressant medications in a class called monoamine oxidase (MAO) inhibitors such as phenelzine and tranylcypromine, narcotic pain relievers such as codeine or propoxyphene, other medicines that affect your brain and spinal cord (CNS depressants), sedative-hypnotics, and tranquilizers such as chlordiazepoxide.

What are the possible side effects of Fioricet?

• • Side effects cannot be anticipated. If any develop or change in intensity, tell your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking this drug.Side effects may include: fatal skin reactions, seizure, confusion, depression, excitement, stomach pain, dizziness, drowsiness, intoxicated feeling, lightheadedness, nausea, sedation, shortness of breath, vomiting, excessive sweating

Can I receive Fioricet if I am pregnant or breastfeeding?

• • The effects of Fioricet during pregnancy and breastfeeding are unknown. Do not breastfeed while taking Fioricet. Tell your doctor immediately if you are pregnant, plan to become pregnant, or are breastfeeding.

What should I do if I miss a dose of Fioricet?

• • Take it as soon as you remember. If it is almost time for your next dose, skip the one you missed and go back to your regular dosing schedule. Do not take two doses at once.

How should I store Fioricet?

• • Store at room temperature in a tight, light-resistant container.

Fioricet 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-dihydroxypropyl) 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.

The in vitro plasma protein binding of butalbital is 45% over the concentration range of 0.5-20 mcg/mL. This falls within the range of plasma protein binding (20%-45%) reported with other barbiturates such as phenobarbital, pentobarbital, and secobarbital sodium. The plasma-to-blood concentration ratio was almost unity, indicating that there is no preferential distribution of butalbital into either plasma or blood cells.

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.

Caffeine

Like most xanthines, caffeine is rapidly absorbed and distributed in all body tissues and fluids, including the CNS, fetal tissues, and breast milk.

Caffeine is cleared through metabolism and excretion in the urine. The plasma half-life is about 3 hours. Hepatic biotransformation prior to excretion results in about equal amounts of 1-methylxanthine and 1-methyluric acid. Of the 70% of the dose that is recovered in the urine, only 3% is unchanged drug.