What it's for (Indications)
- Thiopental, an ultra-short-acting barbiturate, is primarily indicated for the rapid induction of general anesthesia prior to the administration of other anesthetic agents.
- It serves as a valuable hypnotic for short surgical or diagnostic procedures that require a brief period of unconsciousness, such as cardioversion or reduction of dislocations.
- Furthermore, thiopental is employed in the management and control of various convulsive states, including severe status epilepticus, eclampsia, and seizures induced by local anesthetics, where rapid termination of seizure activity is critical.
- Its ability to reduce cerebral metabolic rate for oxygen (CMRO2) and cerebral blood flow makes it a significant agent in neurocritical care for the reduction of elevated intracranial pressure (ICP) in patients with cerebral edema, severe head trauma, or during neurosurgical procedures requiring brain protection and quiet.
- Historically, it has also been used in lower doses for narcoanalysis or narcosynthesis in psychiatric settings, though this application is less common currently.
- The drug's rapid onset and brief duration of action make it suitable for procedures where swift induction and recovery are desired.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | Dosage of thiopental must be highly individualized and titrated meticulously based on the patient's age, weight, physical status, anesthetic requirements, and the concomitant administration of other medications. For adult anesthesia induction, a typical intravenous (IV) dose is 3-5 mg/kg administered over 10-20 seconds, with additional small boluses of 25-50 mg given as necessary to achieve the desired effect. Pediatric induction doses range from 3-6 mg/kg IV, while infants may require 5-8 mg/kg IV, and neonates typically 3-4 mg/kg IV. For the control of convulsive states, initial doses of 75-125 mg IV may be administered, repeated as needed, or a continuous infusion can be initiated, with close monitoring. In the context of intracranial pressure reduction or cerebral protection, a loading dose of 1.5-5 mg/kg IV may be given, followed by a continuous infusion typically ranging from 1-5 mg/kg/hour, carefully titrated to achieve electroencephalographic (EEG) burst suppression or effective ICP control. The drug is generally administered as a 2.5% or 5% solution. Due to its narrow therapeutic index and significant potential for cardiorespiratory depression, careful titration and continuous monitoring of vital signs are paramount. |
Safety & Warnings
Common Side Effects
- Thiopental administration is associated with a range of dose-dependent side effects that require careful monitoring.
- Cardiopulmonary adverse effects are prominent, including significant respiratory depression, which can rapidly progress to apnea, and dose-dependent hypotension resulting from myocardial depression and peripheral vasodilation.
- Reflex tachycardia, cardiac arrhythmias, laryngospasm, bronchospasm, coughing, sneezing, and hiccup may also occur.
- Central nervous system effects can include prolonged somnolence, headache, and rarely, paradoxical excitement or emergence delirium.
- Gastrointestinal disturbances such as nausea and vomiting are less common upon emergence compared to some other anesthetic agents.
- Local reactions at the injection site are a concern due to the drug's high alkalinity, potentially leading to venous thrombosis, phlebitis, pain on injection, and severe tissue necrosis if extravasation occurs.
- Allergic reactions, though rare, can manifest as rash, urticaria, angioedema, or even anaphylaxis.
- Musculoskeletal effects may include involuntary muscle movements or tremors.
- Metabolic disturbances, such as hypokalemia due to intracellular potassium shift, can also be observed.
- The rapid onset and potent effects necessitate vigilant patient assessment.
Serious Warnings
- Black Box Warning: Serious Warnings: Thiopental sodium carries a high risk of significant respiratory depression, including dose-dependent apnea, and profound cardiovascular depression, manifesting as hypotension and reduced cardiac output. These life-threatening adverse effects necessitate that the drug be administered exclusively by, or under the direct supervision of, healthcare professionals extensively trained in general anesthesia, critical care, and advanced airway management. Immediate availability of resuscitation equipment, including positive pressure ventilation devices, oxygen, and pharmacologic support for cardiovascular function, is mandatory. Patients must be continuously monitored for vital signs, including respiratory rate, oxygen saturation, heart rate, and blood pressure, throughout the administration and recovery period. Special caution is required in patients with compromised respiratory or cardiac function, hypovolemia, or those receiving other central nervous system depressants, as these conditions can exacerbate the risks. Rapid intravenous injection or overdose will intensify these severe cardiorespiratory effects. Repeated or prolonged administration can lead to drug accumulation, potentially extending recovery times and prolonging the period of respiratory and cardiovascular vulnerability.
- Thiopental carries several significant warnings that mandate cautious use and close patient monitoring.
- Profound respiratory depression and apnea are common, necessitating immediate availability of resuscitation equipment and personnel capable of providing ventilatory support.
- Significant cardiovascular depression, including hypotension and reduced myocardial contractility, is a critical concern, particularly in patients who are hypovolemic, critically ill, or possess pre-existing cardiovascular instability.
- Extravasation during intravenous administration can lead to severe local pain, tissue damage, and necrosis due to the highly alkaline nature of the solution; immediate management protocols are essential.
- Inadvertent intra-arterial injection is a medical emergency, causing intense pain, vasoconstriction, and potential gangrene, requiring prompt and aggressive intervention.
- Thiopental is absolutely contraindicated in patients with acute intermittent porphyria or variegate porphyria due to its potential to exacerbate these conditions.
- Caution is advised in patients with severe hepatic or renal impairment, as drug clearance may be prolonged, leading to extended duration of action and increased risk of adverse effects.
- Increased sensitivity to thiopental is observed in patients with conditions such as adrenal insufficiency, myxedema, severe anemia, and asthma.
- Furthermore, thiopental readily crosses the placenta and is excreted in breast milk, requiring careful consideration during pregnancy and lactation.
- Prolonged or repeated use can lead to tolerance and physical dependence.
- It significantly potentiates the effects of other central nervous system depressants, opioids, and alcohol, necessitating dosage adjustments of co-administered medications.
How it Works (Mechanism of Action)
Thiopental is an ultra-short-acting barbiturate that exerts its primary pharmacological effects through the modulation of gamma-aminobutyric acid (GABA) receptors in the central nervous system (CNS). GABA is the principal inhibitory neurotransmitter in the brain, and thiopental enhances its inhibitory action. Specifically, thiopental binds to a distinct allosteric site on the GABA-A receptor complex, which is separate from the binding sites for GABA and benzodiazepines. This binding event increases the *duration* of chloride ion channel opening in response to GABA binding, rather than increasing the frequency of opening as benzodiazepines do. The prolonged influx of negatively charged chloride ions into the neuron leads to hyperpolarization of the neuronal cell membrane, rendering the neuron less excitable and effectively reducing its ability to fire action potentials. At very high concentrations, thiopental can also directly activate GABA-A receptors, even in the absence of GABA. Beyond its GABAergic effects, thiopental is also known to inhibit excitatory neurotransmitter systems, such as glutamate at AMPA receptors, and neuronal nicotinic acetylcholine receptors. These combined actions result in a profound dose-dependent depression of CNS activity, leading to sedation, hypnosis, anesthesia, and anticonvulsant effects. A key neuroprotective mechanism involves its capacity to reduce the cerebral metabolic rate for oxygen (CMRO2) and cerebral blood flow (CBF), which leads to cerebral vasoconstriction and a subsequent decrease in intracranial pressure.
Commercial Brands (Alternatives)
No other brands found for this formula.