Phenobarbital 16.2mg Tablets

Phenobarbital is a barbiturate that produces nonselective central nervous system (CNS) depression. It binds to the GABA-A receptor complex at a distinct site from benzodiazepines, enhancing the inhibitory effects of GABA by increasing the duration of chloride channel opening. This leads to hyperpolarization of the neuronal membrane and decreased neuronal excitability. At higher concentrations, it may also inhibit excitatory glutamate receptors and block voltage-gated sodium channels.

Urgent Side Effects: Seek Medical Help Right Away

Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Feeling confused
Change in balance
Muscle spasm
Bad dreams
Restlessness
Hallucinations (seeing or hearing things that are not there)
Shortness of breath
Slow heartbeat
Feeling very tired or weak
Severe dizziness or passing out

Severe Skin Reaction

A severe skin reaction, known as Stevens-Johnson syndrome or toxic epidermal necrolysis, may occur. This condition can cause severe health problems that may not go away and can be life-threatening. Seek medical help immediately if you experience:

Red, swollen, blistered, or peeling skin (with or without fever)
Red or irritated eyes
Sores in your mouth, throat, nose, or eyes

Blood and Liver Disorders

A severe and potentially life-threatening effect has been reported in people taking seizure medications like this one. Contact your doctor right away if you experience:

Swollen glands
Fever
Rash
Painful sores in the mouth or around the eyes
Chest pain
Signs of kidney problems, such as:
+ Unable to pass urine
+ Change in the amount of urine passed
Signs of liver problems, such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Throwing up
+ Yellow skin or eyes

Other Side Effects

Most people do not experience severe side effects, but some may occur. If you notice any of the following side effects, contact your doctor or seek medical help if they bother you or do not go away:

Feeling dizzy or sleepy
Headache
Upset stomach or throwing up
Constipation
Feeling nervous and excitable
* Trouble sleeping

Reporting Side Effects

If you have questions about side effects or want to report any, contact your doctor or call the FDA at 1-800-332-1088. You can also report side effects online at https://www.fda.gov/medwatch.

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the allergic reaction and its symptoms.
Certain health conditions, such as liver disease or breathing difficulties like shortness of breath.
A history of porphyria, a rare genetic disorder.
Heart-related conditions, including:
+ Heart failure
+ Unstable angina (a type of chest pain)
+ Abnormal heartbeat, such as long QT interval on an electrocardiogram (ECG)
+ Kidney disease
+ Low thyroid function (hypothyroidism)
+ Aortic stenosis, a condition characterized by a very narrow heart valve
Recent heart attack
Use of medications that can cause abnormal heart rhythms, specifically prolonged QT interval. Many medications can have this effect, so it is crucial to consult your doctor or pharmacist if you are unsure.

This list is not exhaustive, and it is vital to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist. They will help determine whether it is safe to take this medication with your existing treatments and health status. Never start, stop, or adjust the dosage of any medication without consulting your doctor first.

Important Warnings and Cautions

When taking this medication, it is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, about your treatment.

Risk of Dependence and Withdrawal
The longer you take this medication and the higher the dose, the greater the risk of dependence and withdrawal. Before reducing the dose or stopping the medication, consult your doctor and follow their instructions carefully. Abruptly lowering the dose or stopping the medication can lead to withdrawal, which can be life-threatening. Seek immediate medical attention if you experience any adverse effects.

Tolerance and Dosage
If you have been taking this medication for an extended period or at high doses, you may develop tolerance, requiring higher doses to achieve the same effect. If you notice the medication is not working as well as it previously did, contact your doctor. Do not take more than the prescribed dose.

Monitoring and Precautions
If you are taking this medication long-term, your doctor may recommend regular blood tests to monitor your condition. Discuss this with your doctor. Until you know how this medication affects you, avoid driving and other activities that require alertness. Additionally, refrain from consuming alcohol while taking this medication.

Interactions with Other Substances
Before using marijuana, cannabis, or prescription or over-the-counter medications that may cause drowsiness, consult your doctor. These substances can interact with this medication and increase the risk of adverse effects.

Suicidal Thoughts and Actions
Like other medications used to treat seizures, this medication may rarely increase the risk of suicidal thoughts or actions, particularly in individuals with a history of suicidal ideation. If you experience new or worsening symptoms such as depression, anxiety, restlessness, or mood changes, contact your doctor immediately. If you have suicidal thoughts or actions, seek help right away.

Special Considerations
If you are 65 or older, use this medication with caution, as you may be more susceptible to side effects. When used in children, this medication requires careful monitoring, as the risk of certain side effects may be higher.

Birth Control and Pregnancy
Birth control pills and other hormone-based contraceptives may be less effective while taking this medication. Use two forms of birth control to prevent pregnancy. If you become pregnant or are planning to become pregnant, inform your doctor, as this medication may harm the unborn baby. If you take this medication during the third trimester of pregnancy, your newborn may experience side effects or withdrawal.

Breastfeeding
If you are breastfeeding, consult your doctor to discuss the potential risks to your baby.

Seizure Management
If your seizures change or worsen after starting this medication, consult your doctor to adjust your treatment plan.

• Not typically contraindicated with specific drugs, but caution with severe respiratory depression or porphyria.

• Alcohol and other CNS depressants (e.g., opioids, benzodiazepines, tricyclic antidepressants): Increased CNS depression, respiratory depression, hypotension.
• Valproic acid: Increases phenobarbital serum concentrations (inhibits metabolism), leading to increased toxicity.
• Warfarin: Phenobarbital induces CYP enzymes, decreasing warfarin's anticoagulant effect.
• Oral contraceptives: Phenobarbital induces CYP enzymes, decreasing efficacy of oral contraceptives.
• Griseofulvin: Decreased griseofulvin absorption.
• Doxycycline: Decreased doxycycline half-life.
• Corticosteroids: Decreased corticosteroid efficacy.

• Antihistamines (sedating): Additive CNS depression.
• Antipsychotics: Additive CNS depression.
• Beta-blockers (e.g., metoprolol, propranolol): Phenobarbital may decrease beta-blocker levels.
• Calcium channel blockers (e.g., verapamil, diltiazem): Phenobarbital may decrease CCB levels.
• Digoxin: Phenobarbital may decrease digoxin levels.
• Lamotrigine: Phenobarbital may decrease lamotrigine levels.
• Phenytoin: Variable interaction; can increase or decrease phenytoin levels, or phenobarbital levels.
• Theophylline/Aminophylline: Phenobarbital may decrease xanthine levels.

• Acetaminophen: Increased risk of hepatotoxicity with chronic phenobarbital use.
• Folic acid: Phenobarbital may decrease folic acid levels.

• Excessive drowsiness or sedation
• Dizziness
• Ataxia (unsteadiness, coordination problems)
• Nystagmus (involuntary eye movements)
• Rash or other skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis - rare but serious)
• Changes in mood or behavior (e.g., irritability, hyperactivity, depression)
• Difficulty breathing or shallow breathing
• Unusual bleeding or bruising (rare, hematologic effects)
• Yellowing of skin or eyes (jaundice, liver issues)

Phenobarbital is classified as Pregnancy Category D due to clear evidence of human fetal risk. It is associated with an increased risk of congenital malformations (e.g., cardiac defects, cleft lip/palate) and neonatal withdrawal syndrome.

Phenobarbital is excreted into breast milk and can cause sedation, poor feeding, and withdrawal symptoms in the infant. Use is generally discouraged or requires careful monitoring. Lactation risk is L3 (Moderately Safe) but with significant caution.

Children, especially younger ones, may experience paradoxical hyperactivity or irritability. Close monitoring for behavioral changes is essential. Dosing is weight-based and requires careful titration. Neonates have significantly prolonged half-lives.

Elderly patients are more sensitive to the CNS depressant effects of phenobarbital (e.g., sedation, dizziness, ataxia), increasing the risk of falls and cognitive impairment. Lower initial doses and slower titration are recommended. Monitor renal and hepatic function closely.

• Phenobarbital has a very long half-life, meaning it takes a long time to reach steady state (weeks) and to be eliminated from the body. This allows for once-daily dosing but also means dose adjustments take time to show full effect and toxicity can be prolonged.
• Therapeutic drug monitoring (TDM) is crucial for optimizing efficacy and minimizing toxicity, especially for epilepsy.
• Abrupt discontinuation can precipitate severe withdrawal symptoms, including status epilepticus. Taper slowly over weeks to months.
• It is a potent inducer of many CYP450 enzymes, leading to numerous drug-drug interactions, particularly with oral contraceptives, warfarin, and other antiepileptic drugs.
• Despite its age, phenobarbital remains a valuable, inexpensive antiepileptic, especially for neonatal seizures and refractory epilepsy, but its side effect profile and interaction potential limit its first-line use.

• For epilepsy: Levetiracetam, Valproic acid, Lamotrigine, Carbamazepine, Phenytoin, Topiramate, Oxcarbazepine, Gabapentin, Pregabalin.
• For sedation/insomnia: Benzodiazepines (e.g., lorazepam, zolpidem), Z-drugs (e.g., zolpidem, eszopiclone), Antihistamines (e.g., diphenhydramine), Melatonin.

If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When reporting the incident, be prepared to provide details about the medication taken, the amount, and the time it occurred.