The most frequently reported adverse reactions are drowsiness, lightheadedness,
dizziness, sedation, shortness of breath, nausea, vomiting, abdominal pain,
and intoxicated feeling.
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.
Musculoskeletal: leg pain, muscle fatigue.
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 depedence
Abuse and Dependence
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patients can be withdrawn by using a number of different withdrawal regimens.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.
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