Pentocur (Thiopental)
Thiobarbiturate anesthetic for induction of general anesthesia
Quick Facts About Pentocur
Key Takeaways About Pentocur
- Hospital-only medication: Pentocur is administered exclusively by qualified anesthetic personnel in a clinical setting with resuscitation equipment immediately available
- Ultra-fast onset: Anesthesia begins within 30–40 seconds of intravenous injection, making it suitable for rapid induction
- Multiple clinical uses: Beyond anesthesia induction, it treats acute seizures and reduces dangerously elevated intracranial pressure
- Strict contraindications: Must never be used in patients with porphyria, severe asthma, airway obstruction, myotonic dystrophy, or severe shock
- Significant drug interactions: Interacts with many medications including opioids, benzodiazepines, antidepressants, and antihypertensives – always inform your medical team of all medications you take
What Is Pentocur and What Is It Used For?
Pentocur (thiopental sodium) is an ultra-short-acting thiobarbiturate anesthetic that is injected intravenously to rapidly induce general anesthesia. It is also used as a short-term hypnotic during anesthesia, for the emergency treatment of seizures, and to lower dangerously elevated intracranial pressure in ventilated patients.
Thiopental sodium, the active substance in Pentocur, belongs to the thiobarbiturate class of drugs. These medications work by enhancing the activity of gamma-aminobutyric acid (GABA) at GABA-A receptors in the central nervous system, which produces profound depression of brain activity. This mechanism results in rapid loss of consciousness, making thiopental one of the most widely recognized induction agents in the history of anesthesia.
Once injected intravenously, Pentocur crosses the blood-brain barrier within seconds due to its high lipid solubility, producing unconsciousness in approximately 30 to 40 seconds. The effect of a single bolus dose is brief, typically lasting only 5 to 10 minutes, because the drug is rapidly redistributed from the brain to other tissues such as muscle and fat. However, the drug is metabolized slowly by the liver, which means that repeated doses or continuous infusions can lead to significant accumulation and prolonged effects.
Pentocur is indicated for the following clinical situations:
- Induction of general anesthesia: The primary use of Pentocur is to induce a state of deep unconsciousness (general anesthesia) before surgical procedures. It provides a smooth, rapid onset that allows the anesthesiologist to transition the patient to maintenance anesthesia with other agents such as volatile anesthetics or propofol.
- Short-term hypnosis during anesthesia: In combination with other anesthetic agents, Pentocur can be used to produce sedation during anesthetic procedures where full general anesthesia is not required or as a supplement to regional anesthesia.
- Emergency treatment of seizures: Pentocur is highly effective in terminating seizures, including status epilepticus and convulsions caused by local anesthetic toxicity. Its rapid onset makes it valuable when first-line anticonvulsants such as benzodiazepines have failed.
- Reduction of elevated intracranial pressure (ICP): In intensive care settings, thiopental can be used to lower ICP in patients with traumatic brain injury or other conditions causing cerebral edema, provided the patient is receiving mechanical ventilation.
Pentocur is not a medication you can take at home. It is exclusively administered in hospital or clinical settings by physicians or nurse anesthetists who are specifically trained in airway management and resuscitation. Full resuscitation equipment, including endotracheal intubation apparatus and oxygen, must be immediately available whenever this drug is used.
What Should You Know Before Receiving Pentocur?
Pentocur is contraindicated in patients with porphyria, severe asthma, respiratory obstruction, myotonic dystrophy, and severe cardiovascular shock. Numerous conditions require dose adjustment or special monitoring, and many drug interactions exist that can significantly alter its effects.
Before receiving Pentocur, your medical team will conduct a thorough pre-anesthetic assessment. This includes reviewing your complete medical history, current medications, known allergies, and any previous experiences with anesthesia. It is critically important that you provide your healthcare team with accurate and complete information, as many medical conditions and medications can significantly alter the effects of thiopental.
Contraindications
You must not receive Pentocur if you have any of the following conditions:
- Known allergy to thiopental or other barbiturates: Previous hypersensitivity reactions to any barbiturate drug are an absolute contraindication, as cross-reactivity between barbiturates is common and anaphylactic reactions can be fatal.
- Respiratory obstruction: Any condition that prevents normal airflow, such as upper airway tumors, severe neck swelling, or foreign body obstruction, makes the use of Pentocur extremely dangerous because the drug suppresses respiratory drive and protective airway reflexes.
- Acute severe asthma: Thiopental can trigger bronchospasm and worsen respiratory status. In patients experiencing an acute asthma attack, this drug is absolutely contraindicated.
- Myotonic dystrophy: This hereditary muscle disorder causes paradoxical rigidity with barbiturates, making recovery from anesthesia unpredictable and potentially dangerous.
- Severe cardiovascular shock: The vasodilatory and myocardial depressant effects of thiopental can cause fatal cardiovascular collapse in patients who are already in hemodynamic shock.
- Porphyria: Barbiturates, including thiopental, can precipitate a life-threatening porphyric crisis by inducing the enzyme delta-aminolevulinic acid synthase, leading to accumulation of toxic porphyrin precursors.
Warnings and Precautions
Your anesthesiologist may need to adjust the dose or take additional precautions if you have any of the following conditions:
- Elevated intracranial pressure – while thiopental is used to treat ICP, dosing must be carefully managed
- Asthma or other serious respiratory disease – increased risk of bronchospasm and respiratory depression
- Inflammation of the mouth, jaw, or throat – may lead to difficult airway management
- Cardiovascular disease or hypertension – thiopental causes dose-dependent myocardial depression and vasodilation
- Pericarditis – cardiac tamponade risk increases with cardiovascular depression
- Hypovolemia or dehydration – increased sensitivity to the hypotensive effects
- Severe hemorrhage or burns – altered drug distribution and increased sensitivity
- Myasthenia gravis – increased sensitivity to respiratory depression
- Adrenal insufficiency – even if treated with corticosteroids, dose reduction is needed
- General debility, malnutrition, or significant weight loss – reduced protein binding increases free drug concentration
- Elevated blood urea, toxins, or potassium – altered drug response
- Severe anemia – reduced oxygen-carrying capacity compounds respiratory depression
- Impaired liver or kidney function – reduced metabolism and excretion prolong drug effects
- Metabolic disorders such as thyrotoxicosis, myxedema, or diabetes – unpredictable drug response
- Alcohol dependence or substance use disorder – may require higher induction doses due to cross-tolerance
Pentocur must only be injected into a vein (intravenously). Accidental injection into an artery (intra-arterial) or leakage into surrounding tissue (extravasation) can cause severe tissue damage, including gangrene, and may require amputation. If intra-arterial injection occurs, immediate treatment including vasodilators and heparin is essential to prevent catastrophic tissue ischemia.
Pregnancy and Breastfeeding
Pentocur should only be administered to pregnant women when the physician considers it absolutely necessary and the potential benefits clearly outweigh the risks to the fetus. Thiopental rapidly crosses the placenta and can cause respiratory depression in the newborn, particularly when large doses are given close to delivery. Neonatal resuscitation equipment must be immediately available.
Thiopental is excreted into breast milk. Breastfeeding mothers should temporarily suspend nursing for at least 12 hours after receiving thiopental, or breast milk should be expressed and discarded before administration. This precaution prevents the infant from being exposed to sedative effects through breast milk.
Driving and Operating Machinery
Pentocur has a marked effect on the ability to drive and use machines. Even though the immediate anesthetic effect wears off relatively quickly, you may experience dizziness, confusion, and mental dulling for an extended period after administration. Patients must not drive or operate machinery for 24 to 36 hours after receiving Pentocur. You are personally responsible for assessing whether you are fit to drive or perform activities requiring alertness.
How Does Pentocur Interact with Other Drugs?
Pentocur (thiopental) interacts with a wide range of medications, including opioids, benzodiazepines, antidepressants, antihypertensives, and many others. These interactions can increase sedation, worsen respiratory depression, or cause dangerous drops in blood pressure. Always inform your anesthesiologist of every medication you take.
Thiopental has significant pharmacokinetic and pharmacodynamic interactions with many classes of drugs. The most important interactions are those that increase the depth or duration of central nervous system depression, potentiate cardiovascular effects, or alter the metabolism of thiopental itself. Your anesthesiologist will carefully review your medication list and may adjust doses or choose alternative anesthetic agents based on potential interactions.
| Drug / Drug Class | Effect of Interaction | Clinical Significance |
|---|---|---|
| Opioid analgesics (morphine, fentanyl, sufentanil) | Enhanced CNS depression, respiratory depression, and hypotension | Major – dose reduction required |
| Midazolam and other benzodiazepines | Synergistic sedation and respiratory depression | Major – dose reduction required |
| MAO inhibitors | Prolonged and enhanced CNS depression | Major – use with extreme caution |
| Tricyclic antidepressants (amitriptyline, etc.) | Enhanced sedation and cardiovascular effects | Major – dose adjustment needed |
| Antihypertensives (captopril, enalapril, losartan, etc.) | Potentiated hypotension during induction | Major – careful blood pressure monitoring |
| Aminophylline / Theophylline | May antagonize anesthetic effect, increased risk of seizures | Moderate – may need increased thiopental dose |
| Probenecid | Prolongs thiopental effect by reducing renal clearance | Moderate – dose reduction may be needed |
| Muscle relaxants | Enhanced neuromuscular blockade and respiratory depression | Moderate – standard anesthetic monitoring |
| St. John’s Wort (Hypericum perforatum) | May reduce thiopental effectiveness via enzyme induction | Moderate – inform anesthesiologist |
| Oral anticoagulants | Altered anticoagulant effect due to protein binding displacement | Moderate – monitor coagulation parameters |
Alcohol interaction: Patients who are dependent on or regularly consume large amounts of alcohol may require increased doses of Pentocur due to cross-tolerance with barbiturates. Conversely, acute alcohol intoxication can dramatically enhance the sedative and respiratory depressant effects of thiopental, creating a potentially lethal combination. Always be completely honest with your medical team about your alcohol consumption.
What Is the Correct Dosage of Pentocur?
Pentocur dosing is highly individualized and based on the patient's age, sex, body weight, and overall health status. A test dose is always given first. For anesthesia induction in adults, a typical dose is 3–5 mg/kg administered intravenously. The drug is only administered by qualified anesthetic personnel.
Pentocur will always be administered by trained anesthetic personnel (anesthesiologists or certified nurse anesthetists) who will determine the appropriate dose for your individual situation. The dose is individualized based on multiple factors including your age, sex, body weight, general health status, concurrent medications, and the planned surgical procedure. A small test dose is always administered first to assess your individual response before the full induction dose is given.
Reconstitution
Before administration, Pentocur powder must be reconstituted aseptically with one of the following diluents: sterile water for injection, 0.9% sodium chloride solution, or 5% glucose solution. The most commonly used clinical concentrations are 2.0% or 2.5% solutions. A 3.4% solution in water for injection is isotonic. Concentrations below 2.0% in water are not used as they may cause hemolysis (destruction of red blood cells). Solutions must be freshly prepared and any visible precipitate renders the solution unusable.
| Indication | Typical Adult Dose | Administration | Notes |
|---|---|---|---|
| Anesthesia induction | 3–5 mg/kg IV | Slow IV injection over 20–30 seconds | Test dose given first; additional doses to maintain anesthesia |
| Seizure control | 75–125 mg IV (initial) | Administered as soon as seizure begins | Additional doses may be needed; monitor ventilation |
| Elevated ICP reduction | 1.5–3.5 mg/kg IV | Intermittent bolus doses | Requires mechanical ventilation; monitor ICP |
| Continuous infusion | 0.2%–0.4% solution | Continuous IV drip | For prolonged sedation in ICU; accumulation risk |
Special Populations
Elderly Patients
Older adults are more sensitive to the effects of thiopental due to reduced cardiac output, decreased protein binding, and slower hepatic metabolism. Dose reduction of 30–50% is typically required, with slower administration to avoid profound hypotension.
Patients with Liver or Kidney Impairment
Thiopental is primarily metabolized in the liver. Patients with hepatic impairment will experience prolonged drug effects and require significant dose reduction. Similarly, kidney impairment can affect drug elimination and protein binding, necessitating careful dose titration.
Children
Pediatric dosing is determined by the anesthesiologist based on the child's age, weight, and clinical condition. Children generally require relatively higher doses per kilogram of body weight compared to adults due to their higher cardiac output and different body composition. However, neonates and infants may be more sensitive to the respiratory depressant effects.
Overdose
Overdose with Pentocur is unlikely in clinical settings because the drug is always administered by trained professionals who carefully titrate the dose. However, overdose can occur if injections are given too rapidly or if cumulative doses are excessive. Symptoms of overdose include alarming drop in blood pressure (hypotension), cardiovascular shock, and respiratory arrest. Coughing and respiratory difficulty may also occur, though these can also be signs of inadequate dosing. In case of overdose, administration is immediately stopped and supportive care including airway management, mechanical ventilation, and vasopressor support is initiated.
What Are the Side Effects of Pentocur?
Common side effects of Pentocur include irregular heartbeat, low blood pressure, drowsiness, prolonged recovery from anesthesia, breathing difficulties, coughing, snoring, difficulty swallowing, and shivering. Rare but serious side effects include severe allergic reactions (anaphylaxis) and angioedema. Laryngospasm may occur at the onset of injection.
Like all medications, Pentocur can cause side effects, although not everyone who receives it will experience them. Because thiopental is administered in a controlled clinical environment, most side effects are immediately recognized and managed by the anesthetic team. However, it is important to understand the potential adverse reactions so you can promptly report any unusual symptoms during your recovery.
Tell your doctor or nurse immediately if you experience any of the following: difficulty breathing, wheezing, skin rash, itching, hives, dizziness, swelling of the face, tongue, or throat, difficulty swallowing, or a sudden drop in blood pressure. These may be signs of a severe allergic reaction requiring emergency treatment.
Common Side Effects
May affect up to 1 in 10 patients
- Irregular heartbeat (cardiac arrhythmia)
- Low blood pressure (hypotension)
- Drowsiness and prolonged recovery from anesthesia
- Breathing difficulties and hyperventilation
- Difficulty swallowing
- Coughing and snoring
- Shivering (rigors)
Rare Side Effects
May affect up to 1 in 1,000 patients
- Angioedema (swelling of face, tongue, or throat)
- Anaphylactoid reactions (severe allergic-like reactions)
Frequency Not Known
Reported but frequency cannot be estimated from available data
- Hyperkalemia (elevated blood potassium)
- Hypokalemia (low blood potassium)
- Loss of appetite (anorexia)
- General malaise and weakness
- Fatigue (exhaustion)
- Headache
- Dizziness
- Allergic reactions and skin reactions
- Hypersensitivity reactions
At the onset of Pentocur administration, laryngospasm (spasm of the vocal cords), coughing, or sneezing may occur. Post-operative vomiting is less common with thiopental than with some other anesthetic agents, but persistent drowsiness, confusion, memory loss, and shivering may occur during the recovery period. These effects typically resolve within 24 to 36 hours.
How Should Pentocur Be Stored?
Unopened Pentocur vials require no special storage conditions and should be stored at room temperature. After reconstitution, the solution may be refrigerated (2–8°C) for up to 24 hours or kept at room temperature for a maximum of 6 hours. Solutions with visible precipitate must not be used.
Storage of Pentocur is managed by hospital pharmacy staff and is not a concern for patients receiving the drug. However, understanding proper storage is important for healthcare professionals to ensure drug stability and patient safety.
- Unopened vials: No special storage conditions are required. Store at room temperature, protected from light.
- After reconstitution (refrigerated): Store at 2–8°C for a maximum of 24 hours
- After reconstitution (room temperature): Use within 6 hours
- Multi-patient use: When reconstituted for administration to multiple patients, any unused solution must be discarded after 24 hours
- Visual inspection: Solutions with visible precipitate or particles must not be used
- Keep out of sight and reach of children
- Do not use after the expiration date printed on the carton (EXP)
- Do not autoclave (steam sterilize) the solution
The stability of reconstituted Pentocur depends on the diluent used, storage temperature, and exposure to carbon dioxide. Any factor that lowers the pH of the solution (increased acidity) increases the likelihood of precipitation of thiopental acid. The most stable solutions are those reconstituted with sterile water or isotonic saline and stored refrigerated in tightly sealed containers. Pentocur solutions are incompatible with acidic solutions including suxamethonium, tubocurarine, and other substances with low pH – these must never be mixed in the same syringe or infusion line.
What Does Pentocur Contain?
Pentocur contains thiopental sodium as its active ingredient and sodium carbonate as an excipient. The 0.5 g vial contains 500 mg thiopental sodium (with 51–56 mg sodium), while the 1 g vial contains 1,000 mg thiopental sodium (with 102–112 mg sodium).
Understanding the composition of Pentocur is important, particularly for patients on sodium-restricted diets or those with conditions affected by sodium intake.
Active Ingredient
- Pentocur 0.5 g: Each vial contains 500 mg thiopental sodium (as thiopental sodium and sodium carbonate)
- Pentocur 1 g: Each vial contains 1,000 mg thiopental sodium (as thiopental sodium and sodium carbonate)
Excipient
- Sodium carbonate – used as a buffer to maintain alkaline pH and improve drug solubility
Sodium Content
Pentocur contains clinically significant amounts of sodium:
- 0.5 g vial: Contains 51–56 mg (2.2–2.4 mmol) sodium, equivalent to approximately 2.8% of the WHO recommended maximum daily intake of sodium for adults
- 1 g vial: Contains 102–112 mg (4.4–4.9 mmol) sodium, equivalent to approximately 5.6% of the WHO recommended maximum daily intake of sodium for adults
Packaging
Pentocur is supplied as a white to off-white powder in glass vials with bromobutyl rubber stoppers and aluminum seals, packed in a carton. Available pack sizes:
- 0.5 g: 1, 10, 20, or 50 vials per pack
- 1 g: 1, 10, 20, or 50 vials per pack
Not all pack sizes may be marketed in all countries.
Frequently Asked Questions About Pentocur
Both Pentocur (thiopental) and propofol are intravenous anesthetic agents used for induction of general anesthesia, but they differ significantly. Propofol has largely replaced thiopental in many clinical settings because it provides a smoother induction and faster, clearer recovery with less postoperative nausea. Thiopental has a longer context-sensitive half-life, meaning it accumulates more with repeated dosing. However, thiopental retains important roles in emergency seizure management and intracranial pressure reduction where its specific pharmacological properties are advantageous.
Pentocur is absolutely contraindicated during an acute severe asthma attack because it can cause bronchospasm and further compromise breathing. For patients with well-controlled asthma who are not experiencing an active attack, the anesthesiologist will carefully weigh the risks and benefits. In many cases, an alternative induction agent such as propofol or ketamine may be preferred, as these drugs have less potential to trigger bronchospasm.
While the immediate anesthetic effect of a single dose of Pentocur wears off within 5–10 minutes due to redistribution, residual effects including drowsiness, dizziness, confusion, and mild cognitive impairment can persist for 24 to 36 hours. This is because the drug accumulates in fat tissue and is slowly released and metabolized. You should not drive, operate machinery, or make important decisions during this recovery period.
Pentocur should only be used during pregnancy when the physician considers it absolutely necessary. Thiopental rapidly crosses the placenta and can cause respiratory depression in the newborn. It has been used for cesarean section deliveries when rapid induction is required, but the dose must be carefully limited to minimize neonatal effects. The neonatal team must be prepared for potential respiratory support of the baby. For breastfeeding, nursing should be suspended for at least 12 hours after administration.
Porphyria is a group of metabolic disorders involving the synthesis of heme (a component of hemoglobin). Barbiturates like thiopental strongly induce the enzyme delta-aminolevulinic acid (ALA) synthase, which is the rate-limiting step in heme production. In patients with porphyria, this enzyme induction leads to dangerous accumulation of toxic porphyrin precursors, potentially triggering an acute porphyric crisis with severe abdominal pain, neurological symptoms, psychiatric disturbance, and potentially fatal respiratory paralysis. This makes porphyria an absolute contraindication to all barbiturates.
All information is based on international medical guidelines and peer-reviewed sources including: the European Medicines Agency (EMA) Summary of Product Characteristics, the WHO Model List of Essential Medicines, Miller's Anesthesia (the standard reference textbook for anesthetic pharmacology), European Society of Anaesthesiology and Intensive Care (ESAIC) guidelines, and published systematic reviews on barbiturate anesthetics. All medical claims meet evidence level 1A standards.
References
- World Health Organization. WHO Model List of Essential Medicines – 23rd List (2023). Geneva: WHO; 2023.
- European Medicines Agency. Summary of Product Characteristics: Thiopental Sodium. EMA; Updated 2024.
- Flood P, Rathmell JP, Urman RD. Stoelting's Pharmacology & Physiology in Anesthetic Practice. 6th ed. Philadelphia: Wolters Kluwer; 2022.
- Gropper MA, et al. Miller's Anesthesia. 9th ed. Philadelphia: Elsevier; 2020.
- European Society of Anaesthesiology and Intensive Care (ESAIC). Guidelines on Intravenous Anaesthetic Agents. Eur J Anaesthesiol. 2023.
- British National Formulary (BNF). Thiopental Sodium. National Institute for Health and Care Excellence (NICE). Updated 2024.
- Russo H, Bhestel A. Pharmacology of GABA-A Receptor Ligands in Anesthesiology: A Review. J Clin Pharmacol. 2022;62(3):301–318.
- American Society of Anesthesiologists (ASA). Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology. 2018;128(2):231–249.
Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, which includes board-certified specialists in anesthesiology, clinical pharmacology, and intensive care medicine. Our editorial process follows the GRADE evidence framework, and all content is independently reviewed without commercial funding or pharmaceutical sponsorship.
iMedic Medical Editorial Team – specialists in anesthesiology and clinical pharmacology with documented academic and clinical experience.
iMedic Medical Review Board – independent panel of medical experts reviewing content according to EMA, FDA, and WHO guidelines.
Conflict of Interest: None declared. iMedic receives no pharmaceutical company funding. All content is editorially independent.
Evidence Level: 1A – based on systematic reviews, randomized controlled trials, and international clinical guidelines.
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