Carbrital side effects and drug information

Carbrital comes with a generic name called pentobarbital and carbromal. This medication is classified under a group of drugs called barbiturates.

CAS ID 76-74-4
Molar mass 226.1319 g/mol
ChemSpider ID   4575
Formula C11H18N2O3
Metabolism Liver


These types of drugs function to slow down the activity in the nervous system and the brain. It is used in several different types of treatments.  

Barbiturates are used as hypnotic and sedative agents as it can induce sleep and make you relaxed but not meant to be as a treatment for anxiety. This drug is commonly taken orally.  

This type of medication is also used as an emergency treatment such as for seizure and is used to treat insomnia as well as impotence. Though in this case, the user should only be for a short time.  

To continue its efficacy, Carbrital should not be used for an extended period as it has the potential to lose its effectiveness by the 2nd week of continued usage.

Side Effects

As in any other drug, this medication carries some side effects; that is why the patient must be aware of them before starting with this treatment for nausea.  

The following side effects are based on the experiences of a large number of hospitalized patients.

According to the observation, side effects are more experienced by fully mobile patients. More than 1 in 100 patients experience the most common adverse reaction, and in the ratio of 1:3 per 100 population, the patient experiences lethargy or drowsiness or feel dizzy.

On the other hand, less than 1 in 100 patients have experienced side effects involving the nervous system, respiratory system, cardiovascular system, digestive system, and different types of bodily reactions.

Reactions experienced involving the nervous system 

  • Agitation and Anxiety
  • Confusion
  • Hyperkinesia
  • Ataxia
  • CNS depression
  • Nightmares
  • Nervousness
  • Psychiatric disturbance
  • Hallucinations
  • Insomnia
  • Anxiety
  • Dizziness
  • Thinking abnormally

Respiratory system

  • Hypoventilation
  • Apnea

Cardiovascular system

  • Bradycardia
  • Hypotension
  • Syncope

Digestive system

Other types of side effects

  • Headache
  • Injection site reactions
  • Hypersensitivity reactions
  • Fever
  • Liver damage
  • Megaloblastic anaemia following chronic phenobarbital use

Drug Abuse and Dependence

Barbiturates are known and proven to be habit-forming; that is why Carbrital sodium injection is subject to control by the Federal Controlled Substances Act under DEA Schedule II.

If high doses of this drug are used for an extended time, it may result in either of the following: tolerance in the drug, psychological dependence, or physical addiction.

If more than 400mg of Carbrital or Secobarbital is used every day for about 90 days, the outcome is physical dependence of some degree. And if any of these drugs are used for at least 35 days with a dosage ranging from 600 to 800mg, the likely result is withdrawal seizures.  

Barbiturate addicts consume a dosage of 1.5g every day, and as tolerance developed, thus the need to increase the amount of usage to maintain intoxication.

Some signs of acute intoxication with barbiturates

  • Unsteady gait
  • Slurred speech
  • Sustained nystagmus

Mental signs of chronic intoxication

  • Confusion
  • Poor judgment
  • Irritability
  • Insomnia
  • Somatic complaints

It is also found that symptoms of chronic alcoholism are similar to those of barbiturate dependence. For example, a person is exhibiting signs of alcohol intoxication, but the amount of alcohol in his blood is not proportional to his actions, then barbiturate use would be suspected.

Prolonged and overuse of barbiturates is very dangerous because a lethal dose of it is far less than if with alcohol ingestion. And withdrawal from it can result in some very severe reactions and could even lead to death.

Minor withdrawal symptoms are said to be experienced around 8 to 12 hours after the last dose is taken. 

Some signs of minor withdrawal

  • Anxiety
  • Muscle twitching
  • Tremor of hands and fingers
  • Progressive weakness
  • Drowsiness
  • Distortion in visual perception
  • Nausea
  • Vomiting
  • Insomnia
  • Orthostatic hypotension

When withdrawal is abrupt, significant withdrawal symptoms may happen within 16 hours after the last use, and it is possible to last up to 5 days.

Some symptoms of significant withdrawal

  • Convulsion
  • Delirium

The intensity of withdrawal symptoms gradually decreases within around 15 days. People who are inclined to barbiturate abuse are those who are alcoholics, abusers of some substances such as opiate, amphetamine, and other sedatives- hypnotics.

Barbiturate dependence occurs due to repeated administration done continuously, and the dosage used is way more than the amount required for therapy.  

Some characteristics of barbiturate dependence

  • Strong need to continue taking the drug
  • Having increased dosages
  • Psychic dependence on its effects
  • The physical dependence on its effects thus the need to have the drug

To treat addiction to barbiturates, withdrawal from the medicine must be cautiously and gradually, and the process takes a long time.  

Methods for withdrawal from barbiturates

  • Replacing with a 30mg dosage of phenobarbital for every 100 to 200mg of barbiturates, wherein the total amount of phenobarbital used should not go beyond 600mg daily, and the administration done in 3 to 4 divided dosages.
  • Should there be a symptom of withdrawal on the 1st day of treatment,, an additional 100 to 200mg of phenobarbital may be administered IM along with the oral dose.
  • When phenobarbital is already stabilized, the daily dosage is then decreased by 30mg per day for as long as the process is going smoothly.
  • Adjustments in dosage begin using the patient’s average dose level and then decreasing by 10% daily if the patient can tolerate it.

For infants who are physically dependent on barbiturates, they may be given about 3 to 10mg of phenobarbital per kg per day.  

They are after withdrawal symptoms would be

  • Hyperactivity
  • Disturbed sleep
  • Tremors
  • Hyperreflexia

When the symptoms are relieved, dosage levels of phenobarbital is decreased and should be withdrawn entirely for two weeks.

Indication and dosage

The dosage for Carbrital varies according to different factors such as age, weight, and condition of the patient. By knowing these factors, only then can the appropriate dosage for the patient be determined. 

Also important to note is that parenteral methods should only be when oral administration is not feasible or practical.

Intramuscular Administration

For the IM administration of sodium salts of barbiturates, the injection must be made deeply into a large muscle. It should not be more than 5ml in volume as it may result in tissue irritation.   

The average dose of Carbrital given to a healthy adult is between 150 to 200mg as a single IM administration.

For children, the appropriate dosage is around 2 to 6mg per kg as a single IM injection, and should not be more than 100mg.

Intravenous Administration

The administration of the Carbrital sodium solution should not be combined with any other solution or medication. The use of IV injection is only allowed when other methods are not possible such as when the patient is unconscious or when he or she is resisting like in the state of delirium or when the situation is very urgent.

When doing this method, slow IV injection is necessary because the patient’s vital signs, blood pressure, respiration, and cardiac functions must be carefully observed. Also, when doing IV injection, the devices for resuscitation and artificial ventilation must be present.  

Though the limit of the dosage level for Carbrital sodium has been determined, which is no more than 50mg per minute, there is no specific average IV dose as results vary from each patient.  

When the drug is injected gradually and carefully in fractional doses, there is less risk for overdose and respiratory depression.

For a 70kg adult, the initial dosage is at 100mg, and for younger or debilitated patients, the dosage must be proportionally reduced. A minimum of 1 minute is needed to find out the full effect of the drug. And if there is a need, small increments of the drug may be added, but only up to a maximum of 200 to 500mg for healthy adults.

Anticonvulsant use

In a state of convulsion, Carbrital sodium solution dosage should be kept to a minimum to avoid the occurrence of depression that may come after the convulsion. The injection should be administered slowly, bearing in mind the time needed for the drug to penetrate the blood-brain barrier.

Special Patient Population

For the debilitated or the elderly, and for those with impaired renal function or hepatic disease, the dosage should be reduced as these types of patients are more sensitive to barbiturates.


Parenteral drug products are needed to be visually inspected for discoloration and particulate matter before administration. Solutions for injections that exhibit signs of precipitation should not be used.

Drug Interaction

Barbiturates have been found to have clinically significant drug interactions when used along with phenobarbital. Drug interactions have been found in:

  • Anticoagulants
  • Corticosteroids
  • Griseofulvin
  • Doxycycline
  • Phenytoin, sodium valproate and valproic acid
  • CNS depressants
  • Monoamine Oxidase Inhibitors (MAOI)
  • Estradiol, estrone, progesterone, and other steroidal hormones

Patients that were treated with antiepileptic drug-like phenobarbital became pregnant even while on an oral contraceptive.

Warnings and Precautions

Carbrital comes with several side effects, including impaired reactions and thinking, so if you are taking this drug, do not drive or do any activity that will need you to be alert.

Consuming alcohol, along with this drug, may also cause harmful side effects. And since barbiturates may be habit-forming, do not exceed or prolong this drug’s usage to avoid dependence or addiction.  

Abrupt withdrawal from this drug after prolonged use may lead to severe reactions like delirium, convulsion, or even death. Withdrawal should be gradual.

In IV administration: too rapid administration may lead to apnea, rapid depression, laryngospasm, or vasodilation with a drop in the blood pressure.

Acute or chronic pain: careful administration of barbiturates must be done for those with these kinds of conditions.

Use in pregnancy: pregnant women must not use this drug as it can cause fetal damage. Barbiturates quickly pass into the placental barrier and are distributed throughout fetal tissues.

Women who took barbiturates while in the last trimester of pregnancy affects the infant as the baby may experience withdrawal symptoms.  

Synergistic effects: Do not use this drug if you are allergic to Carbrital or if you have porphyria. And if you have any of these conditions: liver disease, kidney disease, chronic pain, severe asthma or COPD, history of depression, or alcohol addiction, dosage may need to be adjusted.  

If you are pregnant or planning to be while on this treatment, your doctor must be informed.

Because Carbrital may tend to lessen the efficacy of birth control pills, ask your doctor about alternative non-hormone methods.

This drug can easily pass into breastmilk and so should not be used by breastfeeding mothers.

Older adults may also have more risk of experiencing side effects.

Clinical Pharmacology

CNS depressants are barbiturates that may cause sleep induction or mild sedation depending on the dosage.  

High dosage levels of this drug may be implemented when used as an anesthesia.

The risk for this drug is that it can be addictive or habit-forming. Addictive medicines are classified as Controlled Substances by the government, so it is vital that you read the drug manual regarding usage and to be sure that it is not a controlled substance.

Consult your doctor before starting to use this drug.