Pronunciation: pen-toh-BAR-bi-tal Chemical Abstracts Service Registry Number: 76-74-4 Formal Names: Cafergot, Nembutal, Pentobarbitone, Phenobarbitone Informal Names: Nebbies, Nembies, Nemmies, Nimbies, Yellow Bullets, Yellow Dolls, Yellow Jackets, Yellows
Type: Depressant (barbiturate class). See page 20
Federal Schedule Listing: Schedule II (oral and parentral, DEA no. 2270), Schedule III for suppositories (DEA no. 2271)
USA Availability: Prescription
Pregnancy Category: D
Uses. This short-acting substance has sedative qualities but is considered ineffective in treating nervous apprehension. Because of the drug's sleep-inducing characteristics, it is used as a preliminary to administering anesthesia and as a short-term treatment for insomnia. Pentobarbital has been observed to lower blood pressure, body temperature, and muscle tone. The compound can be used as an emergency anticonvulsant when a person has seizures, and has been used to treat alcohol addicts undergoing withdrawal. Pentobarbital has been found effective in reducing pressure that fluid creates in the brain after severe head injury. Pentobarbital reduces a type of nerve cell death called neuronal apoptosis, and this reduction may help prevent stroke. Animal studies indicate that pentobarbital can help protect brain tissue against radiation, which might have practical application during treatment of brain tumors. Veterinarians use the substance for euthanasia: An unusual demonstration of the drug's strength occurred when a lion was poisoned by eating meat from a horse that had been killed with pentobarbital.
Drawbacks. Although the drug is a sedative, it can cause hyperactivity in children. Sudden stoppage of combined pentobarbital and benzodiazepine therapy in an infant caused temporary chorea (involuntary jerking). A feline experiment showed that tremors reminiscent of Parkinson's disease can occur when pentobarbital is administered with chlorpromazine (also called Thora-zine, often used to treat psychotic behavior). Persons with porphyria, a body chemistry affliction that can provoke violence, are supposed to avoid pento-barbital. Examination of epileptic children receiving pentobarbital shows elevated readings for total cholesterol, though levels of high-density lipoprotein
In a monkey experiment pentobarbital interfered with time perception, ability to learn, short-term memory, attention span, and interest in tasks. The substance impeded task performances in a human experiment, with performance getting worse as the amount of thinking necessary for a chore increased. Such a drug is unlikely to be welcome in the workplace. Although children using the substance apparently have trouble with language skills, a study found language development to be normal two years after the medication ceased.
Abuse factors. In a test, alcohol drinkers who were not alcoholics found pentobarbital less appealing than a placebo and experienced no euphoria from pentobarbital, a finding consistent with other studies of persons who do not abuse drugs. When given choices of assorted substances, monkeys chose pen-tobarbital less often than water, which indicates the compound has low addictive potential. In contrast, drug abusers participating in an experiment found effects of pentobarbital and diazepam to be similar. Those two drugs thus had comparable appeal even though scientists running the experiment found pentobarbital possessing only 10% of diazepam's strength. A study testing various effects on former drug addicts found pentobarbital to be 15 times stronger than meprobamate, but morphine acted 6 times stronger than pentobarbital. Cross-tolerance among chlordiazepoxide, pentobarbital, and alcohol has been observed in rats. A study of sedative drug abusers found alcohol and pentobarbital to deliver similar effects, with pentobarbital possibly having more appeal. A monkey experiment indicates that alcohol increases the attractiveness of pentobarbital. Dependence can develop, and in humans the pentobarbital withdrawal syndrome can duplicate the delirium tremens of alcohol withdrawal. A mice study found that tolerance to pentobarbital developed more rapidly if assorted drugs of abuse were also being administered (morphine, amphetamine, alcohol, or cocaine).
Drug interactions. A case report notes that pentobarbital can almost double the speed with which theophylline (commonly used to treat asthma and other breathing difficulties) disappears from the bloodstream, requiring changes in normal theophylline dosage. In a mice experiment alcohol boosted pentobar-bital's potency. A human study found that chronic alcohol ingestion reduces the effective length of a pentobarbital dose. Grapefruit juice extends the amount of sleep produced by pentobarbital in rats, and in mice the drug inhibits caffeine effects. At one time researchers suspected that taking pentobarbital along with MDMA would reduce organic brain damage caused by MDMA, but rat experiments indicate that any apparent benefit comes simply from the lower body temperature produced by pentobarbital. Although cocaine is a stimulant, in a rat experiment it increased the sleep-inducing quality of pentobarbital.
Cancer. In animal experimentation pentobarbital has caused cancer. In humans long-term usage is associated with cancer of the ovaries and bronchi, but that finding is weakened by the patients also smoking cigarettes.
Pregnancy. A large survey of pregnancy outcomes found that pentobarbital does not appear to cause birth defects. Nonetheless pregnant women are supposed to avoid the drug.
Additional information. Some capsule formats of Nembutal (pentobarbital sodium CAS RN 57-33-0) contain FD&C Yellow No. 5 (tartrazine), which can cause asthma attacks or other allergic responses in sensitive persons, particularly if someone has adverse reactions to aspirin. Cafergot PB is a combination of bellafoline, caffeine, and ergotamine tartrate. The combination was tested with and without pentobarbital sodium to determine effect on migraine headache. Presence of pentobarbital not only enhanced reduction of pain but also helped treat anxiety, nausea, vomiting, poor appetite, and low tolerance of light.
Additional scientific information may be found in:
Cole-Harding, S., and H. de Wit. "Self-Administration of Pentobarbital in Light and Moderate Alcohol Drinkers." Pharmacology, Biochemistry, and Behavior 43 (1992): 563-69.
Hambly, G., C. Frewin, and B. Dodd. "Effect of Anticonvulsant Medication in the Preschool Years on Later Language Development." Medical Journal of Australia 148 (1988): 658, 661-62.
Mintzer, M.Z., et al. "Ethanol and Pentobarbital: Comparison of Behavioral and Subjective Effects in Sedative Drug Abusers." Experimental and Clinical Psychophar-macology 5 (1997): 203-15. Pickworth, W.B., M.S. Rohrer, and R.V. Fant. "Effects of Abused Drugs on Psychomotor
Performance." Experimental and Clinical Psychopharmacology 5 (1997): 235-41. Pierce, James I. "Drug-Withdrawal Psychoses." American Journal of Psychiatry 119 (1963): 880-81.
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