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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
General Anesthetic [EPC]
Isoflurane is a halogenated ether used for the induction and maintenance of general anesthesia. It belongs to the class of general inhalation anesthetics and is known for its stability and predictable recovery profile in clinical settings.
Name
Isoflurane
Raw Name
ISOFLURANE
Category
General Anesthetic [EPC]
Drug Count
3
Variant Count
7
Last Verified
February 17, 2026
RxCUI
542347, 542358, 542355
UNII
CYS9AKD70P
About Isoflurane
Isoflurane is a halogenated ether used for the induction and maintenance of general anesthesia. It belongs to the class of general inhalation anesthetics and is known for its stability and predictable recovery profile in clinical settings.
Detailed information about Isoflurane
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Isoflurane.
Isoflurane is a potent, non-flammable inhalation general anesthetic used primarily in the hospital setting to induce and maintain a state of general anesthesia (a medically induced coma with loss of protective reflexes) for surgical procedures. Chemically, it is a halogenated ether, specifically a racemic mixture of (R) and (S) optical isomers. First approved by the U.S. Food and Drug Administration (FDA) in 1981, Isoflurane has remained a cornerstone of modern anesthesiology due to its relative safety, cardiovascular stability, and rapid recovery times compared to older agents like halothane. It is categorized under the pharmacological class of General Anesthetics [EPC] and is typically administered via a calibrated vaporizer as part of a breathing circuit.
Isoflurane belongs to a class of drugs called volatile anesthetics. These substances are liquid at room temperature but are easily converted into a gas for inhalation. Unlike some other anesthetics that may be administered intravenously (through a vein), isoflurane is absorbed through the lungs, allowing for precise control over the depth of anesthesia by adjusting the concentration of the gas the patient breathes. While newer agents like sevoflurane and desflurane have gained popularity for their faster onset, isoflurane remains widely used globally due to its cost-effectiveness and well-documented clinical profile. Your healthcare provider, specifically an anesthesiologist or CRNA (Certified Registered Nurse Anesthetist), will determine the appropriate concentration based on your unique physiological needs.
The exact molecular mechanism of Isoflurane, like most general anesthetics, is complex and involves multiple targets within the central nervous system (CNS). Historically, it was believed that anesthetics worked by dissolving into the lipid bilayer of neuronal membranes (the Meyer-Overton hypothesis). However, modern research indicates that Isoflurane primarily acts by modulating specific ion channels and receptors on the surface of neurons.
At the molecular level, Isoflurane enhances the activity of GABA-A (gamma-aminobutyric acid type A) receptors. GABA is the primary inhibitory neurotransmitter in the brain; by enhancing its effect, Isoflurane increases the flow of chloride ions into neurons, leading to hyperpolarization (making the cell less likely to fire). This results in sedation, amnesia (loss of memory), and unconsciousness. Additionally, Isoflurane inhibits excitatory pathways by antagonizing NMDA (N-methyl-D-aspartate) glutamate receptors and nicotinic acetylcholine receptors. It also acts on glycine receptors in the spinal cord to produce muscle relaxation and immobility in response to surgical stimuli. By targeting these various pathways, Isoflurane ensures that the patient remains unconscious, still, and unaware of pain during surgery.
Isoflurane is FDA-approved for the following indications:
Isoflurane is available only as a sterile liquid for inhalation. It is supplied in 100 mL and 250 mL amber-colored glass bottles. It contains no additives or chemical stabilizers. This liquid must be poured into a specific 'Isoflurane Vaporizer' attached to an anesthesia machine, which precisely converts the liquid into a vapor and mixes it with carrier gases (like oxygen) before delivery to the patient via an endotracheal tube or laryngeal mask airway.
> Important: Only your healthcare provider can determine if Isoflurane is right for your specific condition. It is administered exclusively by trained professionals in a controlled surgical or critical care environment.
Dosage for Isoflurane is not calculated in milligrams like traditional medications; instead, it is measured in MAC (Minimum Alveolar Concentration) units and delivered as a percentage of the inspired gas mixture. One MAC is the concentration of the vapor in the lungs that prevents 50% of patients from moving in response to a surgical incision.
Isoflurane is used in pediatric patients, but special care is required. The MAC for children is higher than for adults, meaning they often require a higher percentage of the gas to achieve the same depth of anesthesia. For example, the MAC in an infant can be as high as 1.6%, whereas in a middle-aged adult, it is approximately 1.15%.
Because Isoflurane is primarily eliminated through the lungs and undergoes minimal metabolism, dose adjustments for patients with kidney disease are generally not required. However, the patient's overall clinical status and fluid balance must be monitored closely during the procedure.
Isoflurane is considered safe for patients with liver disease because only a tiny fraction (0.2%) is processed by the liver. It does not typically cause the liver injury associated with older anesthetics like halothane. No specific dose adjustment is mandated, but the anesthesiologist will monitor liver enzymes if the procedure is exceptionally long.
The MAC for Isoflurane decreases with age. Elderly patients (over 65) generally require significantly lower concentrations to maintain the same level of anesthesia. A decrease of approximately 6% in MAC per decade of life after age 20 is a common clinical rule of thumb. This population is also more susceptible to hypotension (low blood pressure) during administration.
Isoflurane is administered only by inhalation. You will not 'take' this medication yourself.
Because Isoflurane is administered continuously by a healthcare professional during a procedure, there is no possibility of a 'missed dose' in the traditional sense. The flow of the gas is maintained by the anesthesia machine for the duration of the surgery.
An overdose of Isoflurane results in deep anesthesia, which manifests as severe respiratory depression (shallow or stopped breathing) and profound hypotension (dangerously low blood pressure).
> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance. Always inform your anesthesiologist of all medications and supplements you are taking before surgery.
Isoflurane is generally well-tolerated, but because it affects the entire central nervous system and cardiovascular system, several side effects are common during the recovery phase (the 'waking up' period):
While you will be under constant medical supervision while receiving Isoflurane, certain reactions are critical and require immediate intervention by the surgical team:
> Warning: Stop taking Isoflurane and call your doctor immediately if you experience any of these.
There are currently no FDA Black Box Warnings specifically for Isoflurane. However, it carries significant 'Warnings and Precautions' regarding Malignant Hyperthermia and pediatric neurotoxicity that are treated with the same level of clinical gravity as a boxed warning.
Report any unusual symptoms to your healthcare provider. If you have a family history of anesthesia complications, it is vital to disclose this before your procedure.
Isoflurane should only be administered in a facility equipped with full resuscitative equipment and by personnel trained in the administration of general anesthetics. Because it causes a loss of consciousness and suppresses the drive to breathe, continuous monitoring of the patient's vital signs is mandatory. Patients must be monitored for signs of Malignant Hyperthermia, a rare but fatal reaction, throughout the administration and for a period afterward.
No FDA black box warnings for Isoflurane. However, the FDA requires prominent warnings in the labeling regarding the risk of Malignant Hyperthermia and the potential for anesthetic-induced neurotoxicity in young children and during the third trimester of pregnancy.
During and after the administration of Isoflurane, the following must be monitored continuously:
Isoflurane significantly impairs physical and mental capabilities. You must not drive, operate heavy machinery, or make important legal decisions for at least 24 hours after receiving Isoflurane. You must have a responsible adult accompany you home after your procedure.
Alcohol should be avoided for at least 24 hours before and after receiving Isoflurane. Alcohol can enhance the sedative effects of the anesthetic and may increase the risk of respiratory depression or nausea during recovery.
Discontinuation of Isoflurane is managed by the anesthesiologist. As the gas is turned off, the patient begins the 'emergence' phase. Because Isoflurane is eliminated through the lungs, increasing the patient's ventilation (breathing) rate can speed up the waking process. There is no 'withdrawal' syndrome, but patients may experience 'emergence delirium' (confusion or agitation) as they wake up.
> Important: Discuss all your medical conditions, especially any history of heart, liver, or neuromuscular disease, with your healthcare provider before starting Isoflurane.
There are few absolute contraindications for drug combinations with Isoflurane, as it is often used in complex polypharmacy environments. However, certain combinations are avoided due to extreme risk:
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Many 'natural' supplements can have significant effects on how your body responds to anesthesia.
Isoflurane must NEVER be used in the following circumstances:
In these situations, the healthcare provider will weigh the risks against the benefits:
There is a high degree of cross-sensitivity between Isoflurane and other halogenated inhalation anesthetics such as Desflurane and Sevoflurane. If you have had a reaction to one, you are likely to have a reaction to the others. This does not usually apply to intravenous anesthetics like propofol or local anesthetics like lidocaine.
> Important: Your healthcare provider will evaluate your complete medical history, including any family history of anesthesia problems, before prescribing Isoflurane.
It is not known whether Isoflurane is excreted in human milk. However, because it is rapidly eliminated from the mother's body through the lungs (with a very short half-life in the blood), it is generally considered safe to resume breastfeeding once the mother is fully awake and alert. Most professional guidelines suggest that 'pumping and discarding' milk is not necessary after a single exposure to Isoflurane.
Isoflurane is considered safe for patients with kidney failure. Unlike an older anesthetic called methoxyflurane, Isoflurane does not produce enough inorganic fluoride to cause kidney damage (nephrotoxicity). No specific dose adjustments are required based on GFR (Glomerular Filtration Rate).
Patients with liver disease (Child-Pugh Class A, B, or C) can generally receive Isoflurane. Because only 0.2% is metabolized by the liver, it does not typically worsen liver function. However, the drug's effect on blood flow to the liver must be considered during long surgeries.
> Important: Special populations require individualized medical assessment. Always ensure your surgical team is aware of your age, pregnancy status, and any underlying health conditions.
Isoflurane produces a state of general anesthesia through its action on various ion channels in the central nervous system. Its primary target is the GABA-A receptor, where it acts as a positive allosteric modulator. By binding to a specific site on the receptor, it increases the receptor's affinity for GABA, the brain's main inhibitory neurotransmitter. This increases the conduction of chloride ions, leading to neuronal hyperpolarization and reduced excitability.
In addition to GABA, Isoflurane:
| Parameter | Value |
|---|---|
| Bioavailability | 100% (Inhalation) |
| Blood/Gas Partition Coefficient | 1.4 |
| Oil/Gas Partition Coefficient | 99 |
| Metabolism | < 0.2% (Hepatic CYP2E1) |
| Primary Metabolites | Trifluoroacetic acid, Inorganic fluoride |
| Excretion | > 99% Pulmonary (Exhalation) |
| Tmax | Immediate (Steady state reached in minutes) |
Isoflurane is classified as a Volatile Inhalation General Anesthetic. It is part of the halogenated ether family, which also includes Desflurane and Sevoflurane. These agents replaced older anesthetics like ether, chloroform, and halothane because they are non-flammable and have better safety profiles.
Medications containing this ingredient
Common questions about Isoflurane
Isoflurane is a general anesthetic gas used primarily to induce and maintain a state of unconsciousness during major surgical procedures. It is inhaled through a mask or a tube in the throat and works by affecting the central nervous system to ensure the patient does not feel pain or remember the surgery. It is known for providing stable heart and lung function during long operations. Your anesthesiologist will adjust the concentration of the gas throughout the surgery to keep you at the appropriate level of sleep. It is one of the most widely used anesthetics in the world due to its reliability and low cost.
The most common side effects occur during the recovery period as the gas wears off and include nausea, vomiting, and shivering. Some patients may also experience a sore throat, which is often caused by the breathing tube used during the procedure rather than the drug itself. Low blood pressure and a temporary decrease in breathing rate are also common during the surgery but are closely managed by the medical team. Most of these effects are short-lived and resolve within a few hours after the surgery is completed. Your doctor may give you medications to help prevent or treat nausea and shivering.
You should not drink alcohol for at least 24 hours before and 24 hours after receiving Isoflurane anesthesia. Alcohol can interact with the anesthetic and other medications used during surgery, potentially causing dangerous drops in blood pressure or breathing. It can also increase the severity of postoperative nausea and vomiting. Furthermore, alcohol impairs your coordination and judgment, which are already affected by the anesthetic during the recovery phase. Always follow the specific instructions provided by your surgical team regarding alcohol and food consumption. If you have a history of heavy alcohol use, be sure to tell your doctor, as this can change how much anesthetic you need.
Isoflurane is generally reserved for essential surgeries during pregnancy, and its use is carefully evaluated by the medical team. While it is not known to cause birth defects in humans, it is a potent uterine relaxant, which can increase the risk of bleeding during a Cesarean section if used at high doses. There are also concerns about the potential impact of long-term anesthesia (more than 3 hours) on fetal brain development during the third trimester. However, for emergency surgeries, it is often necessary and can be used safely with proper monitoring. Your doctor will discuss the risks and benefits based on the urgency of your procedure. Most short-term exposures for necessary medical reasons are considered acceptable.
Isoflurane works very quickly once it is inhaled, with patients usually losing consciousness within a few minutes if it is used for induction. However, in most modern surgical settings, a faster-acting intravenous medication like propofol is used to put the patient to sleep first, and then Isoflurane is started to keep them asleep. The 'depth' of anesthesia can be adjusted almost instantly by the anesthesiologist by changing the concentration of the vapor in the breathing circuit. Recovery also begins quickly once the gas is turned off, though it may take 10 to 30 minutes for a patient to become fully awake and alert. The exact timing depends on the length of the surgery and the patient's individual metabolism.
Isoflurane is only administered by a healthcare professional during a surgery, and 'stopping' it is a controlled process managed by the anesthesiologist. When the surgery is nearing completion, the doctor will gradually reduce and then turn off the flow of the gas. As you breathe out the remaining vapor, you will slowly regain consciousness. There is no risk of 'withdrawal' in the way there is with addictive drugs, but some patients may experience a period of confusion or agitation called 'emergence delirium' as they wake up. This is a normal part of the process for some people and is monitored closely by the recovery room staff. You do not need to worry about stopping the medication yourself.
It is impossible for a patient to miss a dose of Isoflurane because it is not a medication you take at home. It is administered continuously by an anesthesia machine in a hospital or surgical center. The flow of the gas is monitored every second by an anesthesiologist or nurse anesthetist to ensure you are receiving the exact amount needed for your body size and the type of surgery being performed. If there were any interruption in the delivery of the gas, the medical team would be alerted immediately by alarms on the anesthesia machine. Therefore, you do not need to keep track of doses or worry about missing one.
No, Isoflurane does not cause weight gain. It is a gas used for a short duration during a single surgical event and is almost entirely eliminated from the body through exhalation within hours of the procedure. It does not affect the body's metabolism or fat storage in a way that would lead to weight changes. Any weight changes you notice after surgery are more likely due to IV fluids given during the procedure (which can cause temporary bloating), changes in your diet during recovery, or the physical stress of the surgery itself. If you have concerns about weight changes after a procedure, you should discuss them with your primary care physician.
Isoflurane is almost always used in combination with other medications, such as pain relievers (opioids), muscle relaxants, and sedatives. However, it can interact with some of these drugs, often making them much stronger. For example, it significantly increases the effect of muscle relaxants, so your doctor will use a smaller dose of those drugs. It can also interact with certain heart and blood pressure medications you may already be taking. This is why it is vital to provide your anesthesiologist with a complete list of all prescriptions, over-the-counter drugs, and herbal supplements you use. They will adjust the anesthesia plan to ensure all your medications work safely together.
Yes, Isoflurane is available as a generic medication and is produced by several different pharmaceutical manufacturers. Because it has been on the market since the early 1980s, the patent has long since expired. The generic versions are bioequivalent to the original brand-name version (Forane) and are held to the same strict FDA standards for purity and potency. In most hospitals, the generic version is used because it is highly effective and significantly more cost-effective than newer, brand-name anesthetic gases. You will likely not have a choice in which brand is used, as the hospital typically stocks one specific version for their anesthesia machines.