Fenabbott

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Fenabbott

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Medically reviewed

Rosario Oropesa

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Fenabbott

Property Description
Active Ingredient Phenobarbital (Phenylethylbarbituric Acid)
Pharmacological Class Barbiturate, Central Nervous System (CNS) Depressant
Common Forms Tablet, Elixir, Parenteral Solution
Origin Synthetic (Barbituric Acid Derivative)
General Purpose Stabilization and Generalized Calming of Nerve Activity

Fenabbott is a pharmaceutical preparation whose active component is phenobarbital, a time-tested, synthetic chemical belonging to the barbiturate family. This medication is fundamentally classified as a long-acting Central Nervous System (CNS) Depressant, meaning its core function is to systematically reduce excitability within the brain and spinal cord.

What Type of Medicine is Fenabbott?

Fenabbott, being a trade name for the active ingredient phenobarbital (INN), represents a formulation that is clinically recognized for its extended duration of action compared to many other compounds in the depressant class. Phenobarbital is one of the oldest medications used for nerve stabilization. The classification of Phenobarbital as a CNS depressant places it within a category of substances that create a calming effect by slowing down nerve impulse transmission. As a long-acting compound, it provides a sustained moderation of electrical activity.

Composition and Physical Forms

The medication is a single-ingredient product, containing only phenobarbital as the active constituent, alongside necessary inert components (excipients). Fenabbott is supplied in three distinct dosage forms: the oral tablet, the oral solution (elixir), and a sterile parenteral solution for injection. Phenobarbital is recognized as an essential medicine due to its reliable efficacy as a stabilizing agent. The availability of these forms permits administration via the oral, intravenous (IV), and intramuscular (IM) routes, offering clinical flexibility.

General Therapeutic Purpose

The general therapeutic purpose of Fenabbott is to create a state of stabilization and generalized calming of neuronal activity across the central nervous system. This action is achieved by increasing the influence of the brain's main inhibitory neurotransmitter, GABA. A typical, neutral use scenario involves its application to maintain nerve stability over prolonged periods. The drug's essential benefit is to reduce or prevent the occurrence of abnormal and uncontrolled electrical discharges in the brain, linking its nature as a CNS depressant directly to its utility.

Regulatory References

  1. Phenobarbital - StatPearls (NIH)
  2. Phenobarbital: MedlinePlus Drug Information
  3. Phenobarbital - WHO Essential Medicines List
  4. Phenobarbital - WHO Essential Medicines

What side effects are possible with Fenabbott?

Possible Side Effects and Safety Information

This section describes the officially documented adverse effects and safety characteristics of Fenabbott (phenobarbital), strictly based on governmental regulatory sources, such as the FDA and national drug agencies.


Officially Documented Adverse Reactions

The adverse reactions associated with Fenabbott are often classified by frequency and the affected system-organ class. The most common (occurring in 1-3% of patients) effect documented is somnolence (drowsiness).

Less common (occurring in <1% of patients) effects listed in regulatory labeling across various systems include:

  • Nervous System: Agitation, confusion, ataxia, hyperkinesia, nightmares, and paradoxical excitement (more noted in children and older adults).
  • Cardio-Respiratory: Hypotension, bradycardia, hypoventilation, and syncope.
  • Gastrointestinal: Nausea and vomiting.

Serious Safety Considerations

Official labeling explicitly documents rare but serious adverse reactions, which require specific attention:

  • Severe Dermatologic Reactions: Including Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), which are potentially life-threatening.
  • Systemic Events: Circulatory collapse, severe respiratory depression, and multiorgan hypersensitivity (DRESS).
  • Psychiatric Risk: Association with suicidal behavior and ideation.

Population- and Exposure-Specific Notes

The regulatory profile includes specific safety considerations for certain groups and exposure patterns:

  • Population Notes: Older adults may experience confusion or paradoxical excitement. The drug is associated with potential fetal harm and is present in breast milk. Caution is advised for individuals with severe hepatic or renal impairment.
  • Chronic Use: Long-term exposure is associated with the risk of physical dependence, osteomalacia, and megaloblastic anemia.

Key Restrictions

Fenabbott is a Schedule IV controlled substance. It is contraindicated in patients with conditions such as Acute Intermittent Porphyria and severe respiratory or hepatic disease. Abrupt discontinuation following prolonged use can lead to a severe, life-threatening withdrawal syndrome.

Overdose and Emergency Response

The official regulatory documentation for Fenabbott (phenobarbital) details the high-risk manifestations associated with overdose, which are primarily related to its activity as a long-acting central nervous system (CNS) depressant.

Documented Overdose Presentations

Documented overdose presentations typically include marked CNS depression, ranging from drowsiness and lethargy to stupor and coma. Clinical signs may involve slurred speech, nystagmus, and absent or depressed reflexes. As the overdose progresses, the most serious physiological concerns are the dose-dependent respiratory depression and circulatory collapse, leading to severe hypotension and a state of shock. Life-threatening outcomes documented in regulatory files include pulmonary edema, renal failure, and potentially death. Sensitivity to these CNS effects is officially noted to be increased in patients with uremia.

Required Emergency Action

Management of overdose is defined by the need for symptomatic and supportive therapy, as no specific antidote is known for barbiturate poisoning. Officially described procedures include gastric lavage, intravenous fluids, and dialysis to aid in drug removal. Healthcare providers are mandated to meticulously monitor vital signs.

Immediate medical help is required when severe symptoms are observed. Emergency services must be contacted immediately if the affected person has collapsed, had a seizure, has trouble breathing, or cannot be awakened, as these events represent life-threatening complications as described in government guidance.

Therapeutic Uses of Fenabbott

What Fenabbott Treats: Main Uses and Benefits

Fenabbott is commonly used for its therapeutic benefit in managing conditions marked by increased physiological stress. The medication is applied in therapeutic areas that involve symptomatic relief from convulsive activity and nervous tension.


The core clinical scenarios where Fenabbott is relevant include the long-term management of epilepsy, the acute management of Status Epilepticus, and supportive care during episodes of severe alcohol or benzodiazepine withdrawal. The medication is commonly used to help with nervous tension in clinical settings and may be part of symptomatic management for neonatal seizures and hyperbilirubinemia. Its application provides supportive and generalized calming that supports patients during episodes of heightened discomfort by contributing to easing the overall symptom load during acute crises. It may assist with maintaining a sense of stability when symptoms are more noticeable.


Quick Fact: Relief for Symptoms of Increased Neurological or Muscular Activity

Regulatory References

  1. PHENOBARBITAL tablet - DailyMed - NIH

Eligibility and Restrictions for Use

Eligibility Scope

Populations for whom use is contraindicated: Fenabbott must not be used in patients with known hypersensitivity to barbiturates or any component of the formulation. Absolute prohibitions also apply to individuals with a history of manifest or latent porphyria, marked impairment of liver function, or severe respiratory depression with airway obstruction. Some jurisdictions also list hyperkinetic children as a formal contraindication.

Age-related eligibility and restricted use: Use is established for adults, infants, and children for appropriate indications. However, older adults and debilitated patients require lower doses and special caution due to increased sensitivity and the risk of confusion or oversedation. Pediatric use is cautioned as it may be associated with cognitive deficits. The medicine should be administered cautiously to patients with a history of sedative-hypnotic substance dependence.

Condition-specific and reproductive eligibility: The drug requires caution in patients with hepatic damage and renal impairment. From a reproductive standpoint, Fenabbott is classified as Pregnancy Category D by the US FDA, indicating established human fetal risk, and women of childbearing potential must be apprised of this hazard. The medicine is excreted into breast milk, and caution is formally advised for nursing mothers.

What should I know about interactions with other medicines?

Interactions with other medicines and products

The interaction profile for Fenabbott is largely defined by its metabolism and its potential for additive effects with other agents. Regulatory documents detail several clinically significant interactions, primarily categorized by the mechanism of action.

Pharmacokinetic Interactions

Fenabbott is a substrate for the Cytochrome P450 3A4 (CYP3A4) enzyme. Co-administration with strong CYP3A4 inhibitors, such as Ketoconazole or Ritonavir, results in significantly increased Fenabbott plasma concentrations, necessitating a mandated dose reduction of Fenabbott as described in official labeling. Conversely, strong CYP3A4 inducers, including Rifampin or Phenytoin, can significantly decrease Fenabbott's exposure, making concomitant use not recommended due to potential loss of effectiveness.

Pharmacodynamic Interactions

Product Category Specific Examples (Regulatory Listing) Interaction Restriction
Monoamine Oxidase Inhibitors (MAOIs) Isocarboxazid, Phenelzine Contraindicated; a 14-day washout period is required before initiation.
CNS Depressants Benzodiazepines, Alcohol Use with caution due to additive central nervous system effects.
Anticoagulants Warfarin Increased monitoring is required due to the risk of potentiating bleeding.

These mandated restrictions ensure that co-administration risks—ranging from altered drug exposure to additive adverse effects—are managed according to official government regulatory standards.

Mechanism of Action

Fenabbott acts primarily as a positive allosteric modulator of the gamma-aminobutyric acid type A (GABAA) receptor complex, which is a ligand-gated chloride ion channel predominantly expressed in the central nervous system (CNS) . The drug binds to a distinct site on the GABAA receptor, separate from the endogenous neurotransmitter GABA binding site. This allosteric interaction results in a prolongation of the chloride channel opening time in response to GABA binding. The extended duration of chloride ion influx increases the hyperpolarization of the post-synaptic neuronal membrane. This transmembrane shift elevates the action potential threshold of the neuron, thereby decreasing overall neuronal excitability and suppressing signal propagation. A secondary interaction involves the inhibition of voltage-gated calcium channels, which further restricts the release of excitatory neurotransmitters. The cumulative effect of increased GABAA-mediated inhibitory signaling and decreased excitatory neurotransmission leads to a generalized depression of CNS activity, manifesting as system-level physiological sedation and decreased neuronal firing rate.

Dosage and Administration Information

Instruction Map: How to use Fenabbott — Official Administration Guidelines

The administration of Fenabbott (phenobarbital) is defined by its various official dosage forms and the specific clinical context of use.

Category Instruction
Route of administration The medication is approved for Oral intake (tablet or elixir) for chronic use. The sterile solution is intended for Intramuscular (IM) and strictly controlled Intravenous (IV) administration, the latter being reserved for acute, emergency settings.
Dosing schedule For adult maintenance use, the typical oral regimen is 60 mg to 200 mg per day. For acute management, a parenteral loading dose of 15 mg/kg to 20 mg/kg may be used. The hypnotic dose should not exceed 400 mg in 24 hours.
Age-group administration rules Official labels require a reduced dosage for older adults and debilitated patients due to diminished drug clearance. Pediatric maintenance dosing is based on weight, often ranging from 3 mg/kg to 6 mg/kg per day.

Instruction Classifications (High-level)

Category Classification
Frequency pattern Once daily (long-term maintenance) or in divided doses (for sedation).
Use-context constraints Requires controlled IV administration rate; Mandates dose reduction in specific populations; Requires gradual withdrawal (tapering).

Resulting Procedural Structure

Official instructions define a primary use sequence where the initial dose is carefully set based on age and clinical need. Oral maintenance is often taken at night and should be administered with water. If IV administration is used, the infusion rate must be carefully controlled, officially not exceeding 60 mg per minute in adults. For any long-term regimen, official guidance mandates that the dose must be gradually reduced (tapered) if discontinuation is planned.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Fenabbott

This overview summarizes the types of research and general study findings related to the active ingredient in Fenabbott, phenobarbital. The evidence is presented transparently, describing what has been studied and what remains uncertain, without providing any clinical advice or individual predictions.


Evidence for Use in Long-term Epilepsy Management

Research exploring the long-term use of phenobarbital was evaluated in older Randomized Controlled Trials (RCTs) and meta-analyses focused on adults and children with generalized tonic-clonic and focal seizures. Studies monitored outcomes reflecting daily functioning, specifically monitoring measurements of seizure frequency and monitoring the time intervals between seizure events over prolonged periods. The research basis for this indication has been extensively established, contributing to the historical evidence for symptom stabilization.

Comparative evidence is lacking from recent, large-scale RCTs that would evaluate phenobarbital against newer antiepileptic medications. Due to the historical nature of older trials, long-term effects are not fully established regarding subtle cognitive or behavioral outcomes.


Evidence for Use in Acute Status Epilepticus

Research has explored the use of phenobarbital in managing Status Epilepticus (prolonged seizure activity). Studies, including RCTs and retrospective analyses, tracked outcomes related to acute changes, such as monitoring the occurrence of seizure cessation within a specified time frame in both adult and pediatric patients. Data show patterns in the occurrence of symptom resolution in this crisis setting. What remains uncertain is the balance of acute findings versus associated risks, as the need for interventions like breathing support was observed in some studies.


Evidence for Use in Managing Severe Withdrawal Symptoms

Phenobarbital was studied for supportive care in individuals experiencing severe alcohol or benzodiazepine withdrawal. Research consisted primarily of retrospective chart reviews and cohort studies focused on hospitalized adults. Studies monitored outcomes related to outcomes describing episodic or acute changes, such as observations of the time to reach symptom stability and outcomes related to severe complications, such as delirium tremens. Comparative evidence is lacking from large, prospective RCTs that might evaluate its total body of findings when contrasted with other established protocols.


Evidence in Neonatal and Pediatric Populations

The use of phenobarbital was evaluated in neonates experiencing seizure activity, including RCTs and prospective observational studies. Studies assessed monitoring the occurrence of seizure control in the first few hours or days and also monitored neurodevelopmental outcomes in these children at defined time intervals. Research is ongoing to continuously evaluate the potential difference in long-term effects on brain development when compared to newer antiepileptic drugs.

Key Studies & References

  1. Label: PHENOBARBITAL tablet - DailyMed - NIH (Regulatory/Product Monograph)
  2. Phenobarbital: MedlinePlus Drug Information (Patient Information)
  3. Phenobarbital - eEML - Electronic Essential Medicines List (WHO Status)

Frequently Asked Questions (FAQ)

Common questions about Fenabbott (FAQ)

Q: Are there any common long-term side effects reported for Fenabbott?

Official documents describe the risk of physical dependence associated with chronic use of Fenabbott. Other risks noted in regulatory labeling include osteomalacia (a condition where bones soften) and megaloblastic anemia (a specific type of blood disorder). This information is based on long-term data presented in official sources.

Q: Can older adults typically use Fenabbott?

Fenabbott is typically used in older adults. However, regulatory documents indicate that a reduced dosage is often necessary because these patients may process the medicine more slowly. Official labeling also notes that older individuals may be more likely to experience certain effects, such as increased confusion or paradoxical excitement.

Q: Is there a risk of withdrawal symptoms when stopping Fenabbott?

Yes, regulatory sources mandate that the dose must be gradually reduced (tapered) if discontinuation is planned. Abrupt discontinuation after prolonged use carries the risk of a severe withdrawal syndrome, which may include convulsions and delirium, and can be life-threatening.

Q: Do studies suggest Fenabbott loses its effectiveness over time?

Official documents describe that tolerance may occur with continued use of Fenabbott. This means that over time, the body may require a higher amount of the medicine to achieve the same effect that was originally experienced.

Q: Can Fenabbott be taken with acid reflux medicines?

Regulatory caution is advised because Fenabbott is known to interact with medicines that affect certain liver enzymes (specifically CYP3A4). Since some acid reflux medicines may influence these enzymes, they could change how Fenabbott works in the body.

Q: What happens if a person misses a dose of Fenabbott?

Official patient information describes that if a dose is missed, it can be taken as soon as it is remembered. However, the same instruction clarifies that if it is almost time for the next scheduled dose, the missed dose is to be skipped, and a double dose is not advised.

Q: Does Fenabbott interact with pain relievers like ibuprofen or aspirin?

Regulatory documents advise caution when Fenabbott is used alongside other medicines for acute or chronic pain. This is because these combinations may result in an increased risk of side effects, such as paradoxical excitement or masking of important symptoms.

Q: What information is available about Fenabbott use during breastfeeding?

Fenabbott is known to be excreted into human breast milk. Due to this transfer, regulatory sources describe the need for close monitoring of breastfed infants for potential signs of effects, such as excessive sedation, changes in weight gain, and developmental milestones.

Q: Is Fenabbott the same as other medicines in its class?

Fenabbott is described in official documents as belonging to the barbiturate class of medicines. This group is broadly known as nonselective central nervous system (CNS) depressants, meaning they slow down overall brain activity.

Q: Does Fenabbott treat the underlying cause or just the symptoms?

The official mechanism of action for Fenabbott involves depressing the activity of the central nervous system to reduce neuronal excitability. This action is primarily described as controlling symptoms, such as preventing or treating seizures, rather than addressing the root cause of the condition.

Q: How quickly should I expect Fenabbott to start working?

Fenabbott is described as a long-acting medicine. Regulatory-cited literature indicates that after an oral dose, the drug's highest concentration in the blood (peak plasma concentration) is typically reached 8 to 12 hours later.

Q: Is it common to feel a little dizzy when first starting Fenabbott?

Yes, authoritative patient information lists dizziness as a reported side effect of Fenabbott.

Q: Does Fenabbott affect sleep patterns?

The drug's established function as a central nervous system depressant and sedative indicates it can cause drowsiness. Official documents note that this type of medicine may have an effect on a person's sleep architecture, including a potential rebound in REM sleep upon withdrawal.

Q: What foods or drinks should be avoided while on Fenabbott?

Official patient instructions caution against the consumption of alcohol while taking Fenabbott due to increased depressant effects. Regulatory documents do not list any specific restrictions for general foods or non-alcoholic drinks.

Q: Is it safe to drink alcohol while using Fenabbott?

Official patient information advises that alcohol should not be consumed while taking Fenabbott. Combining the two can result in significantly increased central nervous system depressant effects, which can be severe.

Q: Is Fenabbott a controlled substance?

Yes, Fenabbott and its salts are subject to control under the Federal Controlled Substances Act. Official product information classifies it as a DEA Schedule CIV (Schedule 4) substance.

Q: Can Fenabbott be crushed or split if someone has trouble swallowing pills?

Authoritative patient resources describe that the tablets can be crushed and mixed with food or fluids for individuals who have difficulty swallowing. The instruction also clarifies that the tablet form should not be chewed.

Q: Are there different strengths of Fenabbott available?

Official product labels confirm that Fenabbott is supplied in multiple oral tablet strengths (e.g., 16.2 mg, 32.4 mg, 64.8 mg, and 97.2 mg). This variety allows doctors to adjust the dose as needed.

Q: What is the risk of developing a serious allergic reaction to Fenabbott?

Official documents list the possibility of a severe allergic reaction. Symptoms that have been noted include hives, swelling of the face, eyes, lips, or tongue, and difficulty breathing.

Q: Are there specific symptoms that mean Fenabbott is working?

Fenabbott works by reducing neuronal excitability in the central nervous system. The expected result is typically described as a measurable reduction in seizure frequency or the resolution of an acute seizure event, depending on the use condition.

Q: Is it safe for women who are planning to become pregnant to take Fenabbott?

Official labeling states that this medicine may cause fetal harm. Regulatory sources recommend that if a patient becomes pregnant while taking the drug, they should be informed of the potential risk to the developing fetus.

Q: Are there any known interactions between Fenabbott and herbal remedies?

Patient instructions from regulatory bodies warn about telling a doctor about all other medicines a person is taking, including herbs and vitamins, due to the potential for the product to interact with them.

Q: Does Fenabbott affect blood pressure readings?

Regulatory labels list hypotension (low blood pressure) and bradycardia (slow heart rate) as less common adverse reactions that have been reported.

Q: Can Fenabbott cause skin rashes or sensitivity to the sun?

Official labeling notes the potential for severe skin reactions, including Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN). A general rash is also listed as a symptom of a serious reaction in patient safety information.

Q: Is it possible to become dependent on Fenabbott?

Yes, official documents explicitly state that both physical dependence and psychological dependence may occur with the continued use of Fenabbott.

Q: Does Fenabbott affect blood sugar levels?

Some authoritative patient sources note that individuals with pre-existing conditions like diabetes should use Fenabbott with caution. This suggests the drug has a potential relevance to the regulation of blood sugar.

Q: Do patients need special monitoring while taking Fenabbott?

Yes, regulatory documents advise that doctors will order certain laboratory tests to check the patient's response to Fenabbott. It is necessary to monitor blood levels of the medicine, as dosage adjustments are frequently required.

Q: Why does the official literature mention Fenabbott may not work for everyone?

Official literature describes that patients respond differently to the medicine. Regulatory texts note that the blood levels attained are not completely predictable based on the oral dose, which necessitates monitoring and potential dose adjustment for each person.

Q: Can Fenabbott make existing health conditions worse?

Yes, official labeling lists several health conditions, such as severe respiratory disease or hepatic (liver) disease, where the use of Fenabbott is contraindicated or requires extreme caution due to the potential for making the condition worse.

Q: Can Fenabbott cause mood changes or mental fog?

Official labeling lists confusion, agitation, excitement, and new or increased thoughts of suicide or death as potential adverse reactions. The effect commonly described by users as 'mental fog' is consistent with these documented central nervous system effects.

Q: How long does Fenabbott stay in your system after the last dose?

Fenabbott is known to have a very long half-life. Regulatory-cited literature shows the drug's elimination half-life typically ranges from 53 to 118 hours (approximately 2 to 5 days).

Q: Why are people told to take Fenabbott with food?

Authoritative patient resources note that Fenabbott may be taken with or without food. Official patient resources highlight the importance of consistency with administration from day to day to help maintain steady blood levels of the medicine.

How should Fenabbott be stored and disposed of?

Storage Requirements

Fenabbott (Phenobarbital) must be stored at controlled room temperature, typically 20 C to 25 C (68 F to 77 F), with permitted temperature excursions up to 30 C.

To maintain product stability, regulatory requirements specify that the medicine must be protected from moisture and kept in its original container with the cap tightly closed. The injectable solution must also be protected from light and not frozen.

All forms of Fenabbott must be kept in a secure location, out of the sight and reach of children, as mandated by official labeling.

Disposal Instructions

As a controlled substance, disposal of unused or expired Fenabbott must follow federal and local regulations.

The official instruction for safe disposal is to use an authorized drug take-back program or an official collection site. Disposal into wastewater or household trash is generally discouraged unless specific local instructions permit it after mixing the medicine with an unappealing substance.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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