Phenobarbital Side Effects In Infants And Adults

Last Updated: January 26, 2021

Authored by Roger Weiss, MD

The central phenobarbital effect is stopping seizures from occurring, but the medication also delivers numerous side effects. Most phenobarbital side effects are minor, if unpleasant. However, some side effects of phenobarbital are dangerous and can even become deadly.

Common Phenobarbital Side Effects

Phenobarbital, including the name brand formulations such as Luminal, is known to cause numerous adverse reactions in patients.

Common adverse reactions are similar to those of other medications in the phenobarbital drug class. These include:

  • Phenobarbital urine color changes
  • Dizziness
  • Drowsiness
  • Memory struggles
  • Difficulty concentrating
  • Excitability
  • Irritability
  • Aggression
  • Confusion
  • Loss of coordination
  • Headaches
  • Lethargy
  • Lack of appetite
  • Nausea
  • Vomiting
  • Constipation
  • Hangover effect

Ultimately, these phenobarbital side effects are unpleasant, but they are not debilitating or life-threatening. As such, many patients find that the therapeutic effects of the medication are worth dealing with these side effects of phenobarbital in the short term. In cases where these become phenobarbital long-term side effects, users should speak to their doctor about alternative medications.

Less Common Phenobarbital Side Effects

Phenobarbital adverse effects that are less common may also emerge. These are not life-threatening, but their emergence can indicate that the individual is too sensitive to the medication and needs to switch to an alternative. Less common phenobarbital effects include:

  • Chronic trouble sleeping
  • Nightmares
  • Sensations of spinning
  • Hyperactive behavior
  • Sleepwalking

The prescribing doctor may choose first to alter the phenobarb levels taken to address these symptoms, discontinuing the medication if reduced doses do not eliminate them.

young man sleepwalking

Severe Side Effects Phenobarbital Can Cause

While the majority of Luminal side effects are not dangerous, certain severe adverse reactions are highly concerning, as they can cause long-term damage to the body or even lead to death. The following effects of phenobarbital indicate that the patient should contact their doctor immediately and consider calling emergency services for rapid treatment:

  • Weak or shallow breathing
  • Pain in unusual parts of the body (shoulder, arms)
  • Pale skin
  • Muscle weakness
  • Persistent diarrhea
  • Weight loss
  • Rapid heart rate
  • Numbness or tingling in the hands and feet
  • Abnormally low blood pressure
  • Altered consciousness
  • Decreased blood platelets
  • Decreased bone density
  • Granulocyte deficiency
  • Frequent falling
  • Significant or persistent memory loss
  • Megaloblastic anemia
  • Rickets
  • Stevens-Johnson Syndrome

If the following signs are observed, emergency medical care is vital to survival:

  • Agitation or restlessness
  • Confusion
  • Rapid heart rate
  • High blood pressure
  • Dilated pupils
  • Loss of muscle coordination or twitching muscles
  • Muscle rigidity
  • Heavy sweating
  • Diarrhea
  • Headache
  • Shivering
  • Goosebumps
  • High fever
  • Seizures
  • Unconsciousness

Serve reactions are more likely to be a result of phenobarb toxicity than regular use. As such, those who abuse the medication or attempt phenobarbital suicide are at the most significant risk. However, dangerous reactions can result from normal use as well. Thus all people taking the drug should exercise caution.

Allergy or Intolerance to Phenobarbital

In addition to general phenobarb side effects, there are those that can result from the patient experiencing an allergic reaction. Those who are allergic to other medications in the phenobarb drug class are at the highest risk. However, Luminal side effects caused by allergy can develop in those with no prior allergic reaction, even if they have been taking the medication for some time.

Signs that someone is experiencing a phenobarb allergic reaction include:

  • Hives
  • Breathing struggles
  • Facial swelling, including the eyes, lips, and tongue
  • Throat swelling
  • Burning sensations on the skin or in the eyes
  • A red or purple rash
  • Blistering or peeling of the skin

man with allergy to medication

When someone notes these signs, they should not take another dose of phenobarb and should contact emergency services to be taken to the hospital.

It is important to note that sometimes the allergic reaction is not to the active ingredient in the medication, but the inactive ingredients. In this case, the patient may be able to use the brand name or a different phenobarbital generic name without experiencing allergic reactions. In some cases, this may also reduce the phenobarbital price.

Variables That Impact Phenobarbital Side Effect Emergence

Numerous factors can determine how or if phenobarbital side effects emerge. To a degree, doctors can assess how likely it is that a given patient will experience adverse reactions, but it is not an exact science. Variables that can impact side effect emergence include:

  • Age—phenobarbital side effects in infants and children are more severe than in adults
  • Health status—the presence of other diseases can make it easier for adverse reactions to emerge
  • Other substances—the use of medications, alcohol, and street drugs can all cause side effects to occur
  • Gender—women tend to experience adverse reactions at a higher rate than men
  • Race—certain races may be more likely to experience adverse reactions than others
  • Genetic factors—some people, despite all other variables, are simply more likely to experience adverse reactions

Still, someone could have none of the at-risk variables and still experience side effects. All patients taking the medication should be vigilant.

Methods Reduce or Eliminate Phenobarbital Side Effects

No approach is guaranteed to prevent adverse reactions from occurring. However, some ways can make it more likely that side effects of phenobarbital will be reduced or eliminated. These include:

  • Taking the medication with food
  • Staying hydrated at all times
  • Taking the prescription precisely as indicated
  • Informing the prescribing doctor before taking new medications
  • Never mixing phenobarb with street drugs or alcohol
  • Not taking medicine if the patient is hypersensitive to barbiturates
  • Not taking the medication if liver function is impaired

It is possible that even after considering all the correct steps, the patient will still experience short- or long-term phenobarbital side effects and need to eliminate the use of the medication. Should this be the case, they can work with their doctor to find a healthy alternative.

While anyone can experience side effects while on phenobarbital, those who are at the most considerable risk are the individuals who abuse the medication. Anyone who is taking phenobarb recreationally or at higher doses than prescribed needs help to get clean. By contacting a drug and alcohol rehab center, those abusing the medication can get off it and live a better life.

Page Sources

  1. PHENOBARBITAL- phenobarbital tablet. U.S. National Library of Medicine.
  2. Muaed Jamal Alomar. Factors affecting the development of adverse drug reactions (Review article). Saudi Pharm J. 2014 Apr; 22(2): 83–94.

Published on: July 3rd, 2019

Updated on: January 26th, 2021

About Author

Roger Weiss, MD

Dr. Roger Weiss is a practicing mental health specialist at the hospital. Dr. Weiss combines his clinical practice and medical writing career since 2009. Apart from these activities, Dr. Weiss also delivers lectures for youth, former addicts, and everyone interested in topics such as substance abuse and treatment.


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