SIDE EFFECTS
The following adverse reactions and their incidences were compiled from surveillance of thousands of hospitalized patients who received barbiturates. Because such patients may be less aware of some of the milder adverse effects of barbiturates, the incidence of these reactions may be somewhat higher in fully ambulatory patients.
More than 1 in 100 Patients
The most common adverse reaction estimated to occur at a rate of 1 to 3 patients
per 100 is the following:
Nervous System: Somnolence
Less than 1 in 100 Patients
Adverse reactions estimated to occur at a rate of less than 1 in 100 patients
are listed below, grouped by organ system and by decreasing order of occurrence:
Nervous System: Agitation, confusion, hyperkinesia, ataxia, CNS depression, nightmares, nervousness, psychiatric disturbance, hallucinations,
insomnia, anxiety, dizziness, abnormality in thinking
Respiratory System: Hypoventilation, apnea
Cardiovascular System: Bradycardia, hypotension, syncope
Digestive System: Nausea, vomiting, constipation
Other Reported Reactions: Headache, injection site reactions,
hypersensitivity reactions (angioedema, skin rashes, exfoliative dermatitis),
fever, liver damage, megaloblastic anemia following chronic phenobarbital use
Drug Abuse And Dependence
Abuse and addiction are separate and distinct from physical dependence and
tolerance. Abuse is characterized by misuse of the drug for non-medical purposes,
often in combination with other psychoactive substances. Physical dependence
is a state of adaptation that is manifested by a specific withdrawal syndrome
that can be produced by abrupt cessation, rapid dose reduction, decreasing blood
level of the drug and/or administration of an antagonist. Tolerance is a state
of adaptation in which exposure to a drug induces changes that result in a diminution
of one or more of the drug's effects over time. Tolerance may occur to both
the desired and undesired effects of drugs and may develop at different rates
for different effects.
Addiction is primary, chronic, neurobiological disease with genetic, psychosocial,
and environmental factors influencing its development and manifestations. It
is characterized by behaviors that include one or more of the following: impaired
control over drug use, compulsive use, continued use despite harm, and craving.
Drug addiction is a treatable disease, utilizing a multidisciplinary approach,
but relapse is common.
Controlled substance
Seconal Sodium (secobarbital sodium capsules) Capsules are a Schedule II drug.
Dependence
Barbiturates may be habit-forming; tolerance, psychological dependence, and
physical dependence may occur, especially following prolonged use of high doses
of barbiturates. Daily administration in excess of 400 mg of secobarbital for
approximately 90 days is likely to produce some degree of physical dependence.
A dosage of 600 to 800 mg for at least 35 days is sufficient to produce withdrawal
seizures. The average daily dose for the barbiturate addict is usually about
1.5 g. 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 twofold. As this occurs, the margin between intoxicating
dosage and fatal dosage becomes smaller.
Symptoms of acute intoxication with barbiturates include unsteady gait, slurred speech, and sustained nystagmus. Mental signs of chronic intoxication include confusion, poor judgment, irritability, insomnia, and somatic complaints.
Symptoms of barbiturate dependence are similar to those of chronic alcoholism.
If an individual appears to be intoxicated with alcohol to a degree that is
radically disproportionate to the amount of alcohol in his or her blood, the
use of barbiturates should be suspected. The lethal dose of a barbiturate is
far less if alcohol is also ingested.
The symptoms of barbiturate withdrawal can be severe and may cause death. Minor withdrawal symptoms may appear 8 to 12 hours after the last dose of a barbiturate. These symptoms usually appear in the following order: anxiety, muscle twitching, tremor of hands and fingers, progressive weakness, dizziness, distortion in visual perception, nausea, vomiting, insomnia, and orthostatic hypotension. Major withdrawal symptoms (convulsions and delirium) may occur within 16 hours and last up to 5 days after abrupt cessation of barbiturates. Intensity of withdrawal symptoms gradually declines over a period of approximately 15 days. Individuals susceptible to barbiturate abuse and dependence include alcoholics and opiate abusers, as well as other sedative-hypnotic and amphetamine abusers.
Drug dependence on barbiturates arises from repeated administration on a continuous basis, generally in amounts exceeding therapeutic dose levels. The characteristics of drug dependence on barbiturates include the following: (a) a strong desire or need to continue taking the drug; (b) a tendency to increase the dose; (c) a psychic dependence on the effects of the drug related to subjective and individual appreciation of those effects; and (d) a physical dependence on the effects of the drug, requiring its presence for maintenance of homeostasis and resulting in a definite, characteristic, and self-limited abstinence syndrome when the drug is withdrawn. Treatment of barbiturate dependence consists of cautious and gradual withdrawal of the drug. Barbiturate-dependent patients can be withdrawn by using a number of withdrawal regimens. In all cases, withdrawal takes an extended period. One method involves substituting a 30 mg dose of phenobarbital for each 100 to 200 mg dose of barbiturate that the patient has been taking. The total daily amount of phenobarbital is then administered in 3 or 4 divided doses, not to exceed 600 mg daily. Should signs of withdrawal occur on the first day of treatment, a loading dose of 100 to 200 mg of phenobarbital may be administered IM in addition to the oral dose. After stabilization on phenobarbital, the total daily dose is decreased by 30 mg a day as long as withdrawal is proceeding smoothly. A modification of this regimen involves initiating treatment at the patient's regular dosage level and decreasing the daily dosage by 10% as tolerated by the patient.
Infants that are physically dependent on barbiturates may be given phenobarbital,
3 to 10 mg/kg/day. After withdrawal symptoms (hyperactivity, disturbed sleep,
tremors, and hyperreflexia) are relieved, the dosage of phenobarbital should
be gradually decreased and completely withdrawn over a 2-week period.