Nembutal (pentobarbital sodium)

Common side effects of Nembutal include:

• problems with memory or concentration,
• excitement,
• irritability,
• aggression (especially in children or older adults),
• confusion,
• loss of balance or coordination,
• nightmares,
• nausea,
• vomiting,
• constipation,
• headache,
• drowsiness,
• "hangover" effect (drowsiness the day after a dose),
• agitation,
• nervousness,
• insomnia,
• anxiety,
• dizziness,
• low blood pressure,
• injection site reactions, or
• skin rash.

Seek medical attention immediately if you suffer from any serious side effects of Nembutal such as:

• hallucinations,
• weak or shallow breathing,
• slow heart rate,
• weak pulse, or
• feeling like you might pass out.

DO NOT USE IF MATERIAL HAS PRECIPITATED

Dosages of barbiturates must be individualized with full knowledge of their particular characteristics and recommended rate of administration. Factors of consideration are the patient's age, weight, and condition. Parenteral routes should be used only when oral administration is impossible or impractical.

Intramuscular Administration

• IM injection of the sodium salts of barbiturates should be made deeply into a large muscle, and a volume of 5 mL should not be exceeded at any one site because of possible tissue irritation.
• After IM injection of a hypnotic dose, the patient's vital signs should be monitored.
• The usual adult dosage of Nembutal Sodium Solution is 150 to 200 mg as a single IM injection; the recommended pediatric dosage ranges from 2 to 6 mg/kg as a single IM injection not to exceed 100 mg.

Intravenous Administration

• Nembutal Sodium Solution should not be admixed with any other medication or solution. IV injection is restricted to conditions in which other routes are not feasible, either because the patient is unconscious (as in cerebral hemorrhage, eclampsia, or status epilepticus), or because the patient resists (as in delirium), or because prompt action is imperative.
• Slow IV injection is essential, and patients should be carefully observed during administration.
• This requires that blood pressure, respiration, and cardiac function be maintained, vital signs be recorded, and equipment for resuscitation and artificial ventilation be available.
• The rate of IV injection should not exceed 50 mg/min for pentobarbital sodium.
• There is no average intravenous dose of Nembutal Sodium Solution (pentobarbital sodium injection) that can be relied on to produce similar effects in different patients. The possibility of overdose and respiratory depression is remote when the drug is injected slowly in fractional doses.
• A commonly used initial dose for the 70 kg adult is 100 mg. Proportional reduction in dosage should be made for pediatric or debilitated patients.
• At least one minute is necessary to determine the full effect of intravenous pentobarbital.
• If necessary, additional small increments of the drug may be given up to a total of from 200 to 500 mg for normal adults.

Anticonvulsant Use

• In convulsive states, dosage of Nembutal Sodium Solution should be kept to a minimum to avoid compounding the depression which may follow convulsions.
• The injection must be made slowly with due regard to the time required for the drug to penetrate the blood-brain barrier.

Special Patient Population

• Dosage should be reduced in the elderly or debilitated because these patients may be more sensitive to barbiturates. Dosage should be reduced for patients with impaired renal function or hepatic disease.

Inspection

• Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution containers permit. Solutions for injection showing evidence of precipitation should not be used.

Most reports of clinically significant drug interactions occurring with the barbiturates have involved phenobarbital. However, the application of these data to other barbiturates appears valid and warrants serial blood level determinations of the relevant drugs when there are multiple therapies.

Anticoagulants

• Phenobarbital lowers the plasma levels of dicumarol (name previously used: bishydroxycoumarin) and causes a decrease in anticoagulant activity as measured by the prothrombin time. Barbiturates can induce hepatic microsomal enzymes resulting in increased metabolism and decreased anticoagulant response of oral anticoagulants (e.g., warfarin, acenocoumarol, dicumarol, and phenprocoumon).
• Patients stabilized on anticoagulant therapy may require dosage adjustments if barbiturates are added to or withdrawn from their dosage regimen.

Corticosteroids

• Barbiturates appear to enhance the metabolism of exogenous corticosteroids probably through the induction of hepatic microsomal enzymes.
• Patients stabilized on corticosteroid therapy may require dosage adjustments if barbiturates are added to or withdrawn from their dosage regimen.

Griseofulvin

• Phenobarbital appears to interfere with the absorption of orally administered griseofulvin, thus decreasing its blood level.
• The effect of the resultant decreased blood levels of griseofulvin on therapeutic response has not been established. However, it would be preferable to avoid concomitant administration of these drugs.

Doxycycline

• Phenobarbital has been shown to shorten the half-life of doxycycline for as long as 2 weeks after barbiturate therapy is discontinued.
• This mechanism is probably through the induction of hepatic microsomal enzymes that metabolize the antibiotic.
• If phenobarbital and doxycycline are administered concurrently, the clinical response to doxycycline should be monitored closely.

Phenytoin, Sodium Valproate, Valproic Acid

• The effect of barbiturates on the metabolism of phenytoin appears to be variable.
• Some investigators report an accelerating effect, while others report no effect.
• Because the effect of barbiturates on the metabolism of phenytoin is not predictable, phenytoin and barbiturate blood levels should be monitored more frequently if these drugs are given concurrently.
• Sodium valproate and valproic acid appear to decrease barbiturate metabolism; therefore, barbiturate blood levels should be monitored and appropriate dosage adjustments made as indicated.

Central Nervous System Depressants

• The concomitant use of other central nervous system depressants, including other sedatives or hypnotics, antihistamines, tranquilizers, or alcohol, may produce additive depressant effects.

Monoamine Oxidase Inhibitors (MAOI)

• MAOI prolong the effects of barbiturates probably because metabolism of the barbiturate is inhibited.

Estradiol, Estrone, Progesterone And Other Steroidal Hormones

• Pretreatment with or concurrent administration of phenobarbital may decrease the effect of estradiol by increasing its metabolism.
• There have been reports of patients treated with antiepileptic drugs (e.g., phenobarbital) who became pregnant while taking oral contraceptives.
• An alternate contraceptive method might be suggested to women taking phenobarbital.

Drug Abuse And Dependence

• Pentobarbital sodium injection is subject to control by the Federal Controlled Substances Act under DEA schedule II.
• 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 milligrams (mg) of pentobarbital or secobarbital for approximately 90 days is likely to produce some degree of physical dependence. A dosage of from 600 to 800 mg taken for at least 35 days is sufficient to produce withdrawal seizures.
• The average daily dose for the barbiturate addict is usually about 1.5 grams.
• 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 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 these drugs. 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 to barbiturates arises from repeated administration of a barbiturate or agent with barbiturate-like effect on a continuous basis, generally in amounts exceeding therapeutic dose levels.
• The characteristics of drug dependence to barbiturates include:
  •  (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 different withdrawal regimens.
• In all cases withdrawal takes an extended period of time. 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 to 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 percent if tolerated by the patient.
• Infants physically dependent on barbiturates may be given phenobarbital 3 to 10 mg/kg/day. After withdrawal symptoms (hyperactivity, disturbed sleep, tremors, hyperreflexia) are relieved, the dosage of phenobarbital should be gradually decreased and completely withdrawn over a 2-week period.

• 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.
• 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.
• Caution should be exercised when a barbiturate is administered to a nursing woman since small amounts of barbiturates are excreted in the milk.