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- Habit forming: Barbiturates may be habit forming. Tolerance, psychological and physical dependence may occur with continued use. (See "Drug Abuse and Dependence" and "Pharmacokinetics" sections). Patients who have psychological dependence on barbiturates may increase the dosage or decrease the dosage interval without consulting a physician and may subsequently develop a physical dependence on barbiturates. To minimize the possibility of overdosage or the development of dependence, the prescribing and dispensing of sedative-hypnotic barbiturates should be limited to the amount required for the interval until the next appointment. Abrupt cessation after prolonged use in the dependent person may result in withdrawal symptoms, including delirium, convulsions, and possibly death. Barbiturates should be withdrawn gradually from any patient known to be taking excessive dosage over long periods of time. (See "Drug Abuse and Dependence" section).
- IV administration: Too rapid administration may cause respiratory depression, apnea, laryngospasm, or vasodilation with fall in blood pressure.
- Acute or chronic pain: Caution should be exercised when barbiturates are administered to patients with acute or chronic pain, because paradoxical excitement could be induced or important symptoms could be masked. However, the use of barbiturates as sedatives in the postoperative surgical period and as adjuncts to cancer chemotherapy is well established.
- Use in pregnancy: Barbiturates can cause fetal damage when
administered to a pregnant woman. Retrospective, case-controlled studies have
suggested a connection between the maternal consumption of barbiturates and
a higher than expected incidence of fetal abnormalities. Following oral or
parenteral administration, barbiturates readily cross the placental barrier
and are distributed throughout fetal tissues with highest concentrations found
in the placenta, fetal liver, and brain. Fetal blood levels approach maternal
blood levels following parenteral administration.
Withdrawal symptoms occur in infants born to mothers who receive barbiturates throughout the last trimester of pregnancy. (See "Drug Abuse and Dependence" section). If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.
- Synergistic effects: The concomitant use of alcohol or other CNS depressants may produce additive CNS depressant effects.
Barbiturates may be habit forming. Tolerance and psychological and physical dependence may occur with continuing use. (See "Drug Abuse and Dependence" section). Barbiturates should be administered with caution, if at all, to patients who are mentally depressed, have suicidal tendencies, or a history of drug abuse.
Elderly or debilitated patients may react to barbiturates with marked excitement, depression, and confusion. In some persons, barbiturates repeatedly produce excitement rather than depression.
In patients with hepatic damage, barbiturates should be administered with caution and initially in reduced doses.
Parenteral solutions of barbiturates are highly alkaline. Therefore, extreme care should be taken to avoid perivascular extravasation or intra-arterial injection. Extravascular injection may cause local tissue damage with subsequent necrosis; consequences of intra-arterial injection may vary from transient pain to gangrene of the limb. Any complaint of pain in the limb warrants stopping the injection.
Prolonged therapy with barbiturates should be accompanied by periodic laboratory evaluation of organ systems, including hematopoietic, renal, and hepatic systems. (See "PRECAUTIONS -General" and "ADVERSE RECATIONS" sections).
- Animal data. Phenobarbital sodium is carcinogenic in mice and rats after lifetime administration. In mice, it produced benign and malignant liver cell tumors. In rats, benign liver cell tumors were observed very late in life.
- Human data. In a 29-year epidemiological study of 9,136 patients
who were treated on an anticonvulsant protocol that included phenobarbital,
results indicated a higher than normal incidence of hepatic carcinoma. Previously,
some of these patients were treated with thorotrast, a drug that is known
to produce hepatic carcinomas. Thus, this study did not provide sufficient
evidence that phenobarbital sodium is carcinogenic in humans.
Data from one retrospective study of 235 children in which the types of barbiturates are not identified suggested an association between exposure to barbiturates prenatally and an increased incidence of brain tumor. (Gold, E., et al., "Increased Risk of Brain Tumors in Children Exposed to Barbiturates," Journal of National Cancer Institute, 61:1031-1034, 1978).
- Teratogenic effects. Pregnancy Category D-See "WARNINGS-Use in Pregnancy" section.
- Nonteratogenic effects. Reports of infants suffering from long-term barbiturate exposure in utero included the acute withdrawal syndrome of seizures and hyperirritability from birth to a delayed onset of up to 14 days. (See "Drug Abuse and Dependence" section).
Labor and delivery
Hypnotic doses of these barbiturates do not appear to significantly impair uterine activity during labor. Full anesthetic doses of barbiturates decrease the force and frequency of uterine contractions. Administration of sedative-hypnotic barbiturates to the mother during labor may result in respiratory depression in the newborn.
Premature infants are particularly susceptible to the depressant effects of barbiturates. If barbiturates are used during labor and delivery, resuscitation equipment should be available.
Data are currently not available to evaluate the effect of these barbiturates when forceps delivery or other intervention is necessary. Also, data are not available to determine the effect of these barbiturates on the later growth, development, and functional maturation of the child.
Caution should be exercised when a barbiturate is administered to a nursing woman since small amounts of barbiturates are excreted in the milk.
No adequate well-controlled studies have been conducted in pediatric patients; however, safety and effectiveness of pentobarbital in pediatric patients is supported by numerous studies and case reports cited in the literature. Pediatric dosing information for Nembutal is described in the DOSAGE AND ADMINISTRATION section.
Clinical studies of Nembutal (pentobarbital) have not included sufficient numbers of subjects aged 65 and over to determine whether elderly subjects respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.
Elderly patients may react to barbiturates with marked excitement, depression, and confusion. In some persons, barbiturates repeatedly produce excitement rather than depression. Dosage should be reduced in the elderly because these patients may be more sensitive to barbiturates.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 7/2/2008
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