SIDE EFFECTS
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 System: 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 System: 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patients can be withdrawn by using a number of different withdrawal regimens.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.
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.