FORANE
Clinical safety rating
cautionComprehensive clinical and safety monograph for FORANE (FORANE).
Enhances GABA-A receptor activity and inhibits glutamate receptors, leading to neuronal hyperpolarization and anesthesia.
| Metabolism | Primarily hepatic via CYP2E1; also undergoes glucuronidation and defluorination. |
| Excretion | Primarily exhaled unchanged via lungs (>95%); <5% metabolized in liver to fluoride ions and other metabolites, which are excreted renally. |
| Half-life | Context-sensitive half-life: 2-5 minutes after short exposure; prolonged to 30-60 minutes after prolonged administration due to accumulation in fat and muscle. Terminal elimination half-life: 0.5-1 hour. |
| Protein binding | ~40% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Vd: 1.5-2.0 L/kg, reflecting distribution to highly perfused tissues (brain, heart, liver, kidneys) and subsequent redistribution to muscle and fat. |
| Bioavailability | 100% via inhalation. |
| Onset of Action | Inhalation: loss of consciousness within 1-2 minutes at appropriate vaporizer settings. |
| Duration of Action | Rapidly reversible; recovery of consciousness occurs within 5-10 minutes after discontinuation. Clinical duration depends on depth and duration of anesthesia. |
| Molecular Weight | 184.5 |
| Action Class | General anaesthetic agents |
| Brand Substitutes | Isoflurane Usp Liquid For Inhalation, Isotroy Solution for inhalation, Isorane Liquid For Inhalation |
Induction: 0.5-3% inspired; Maintenance: 0.5-2% inspired.
| Dosage form | LIQUID |
| Renal impairment | No adjustment required. |
| Liver impairment | Use with caution; reduce dose in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Induction: 1-4% inspired; Maintenance: 0.5-2% inspired. |
| Geriatric use | Reduce inspired concentrations by 25-50% due to increased sensitivity. |
| 1st trimester | Avoid elective use; animal studies show teratogenicity at high doses. Limited human data. |
| 2nd trimester | Use only if clearly needed; may cause maternal hypotension and fetal acidosis. |
| 3rd trimester | Use caution; may cause uterine relaxation and neonatal depression if used near delivery. |
Clinical note
Comprehensive clinical and safety monograph for FORANE (FORANE).
| Placental transfer | Rapidly crosses placenta; fetal concentrations approximate maternal within minutes. |
| Breastfeeding | Excreted in breast milk in low concentrations. Limited data; monitor infant for sedation. Use caution. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FORANE (isoflurane) is classified as FDA Category C. In first trimester, animal studies show fetal malformations at high doses; human data insufficient. Second and third trimesters: known to cause dose-dependent maternal hypotension and uterine relaxation, which may reduce placental perfusion; use only if clearly needed. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, oxygen saturation, end-tidal CO2, and depth of anesthesia. Fetal heart rate monitoring should be performed when feasible. Uterine tone and contractility should be assessed, especially in third trimester due to uterine relaxant effects. |
| Fertility Effects | No known significant effects on fertility in humans. In animal studies, prolonged exposure to high concentrations may cause reproductive toxicity. Occupational exposure to waste anesthetic gases may reduce fertility in female personnel. |
■ FDA Black Box Warning
None
| Serious Effects |
Known or suspected genetic susceptibility to malignant hyperthermiaHistory of severe hepatic toxicity after previous halothane anesthesiaHypersensitivity to isoflurane or other halogenated anesthetics
| Precautions | Risk of malignant hyperthermia, Respiratory depression, Hypotension, Hepatotoxicity with repeated use or in susceptible patients, Nephrotoxicity due to fluoride ions |
| Food/Dietary | No specific food interactions are documented for isoflurane. However, patients should follow standard preoperative fasting guidelines (e.g., NPO for 8 hours prior to elective surgery) to reduce aspiration risk during anesthesia. |
| Clinical Pearls | FORANE (isoflurane) is a potent inhalational anesthetic with rapid onset and offset due to low blood-gas solubility. It causes dose-dependent respiratory depression and hypotension via peripheral vasodilation. Monitor end-tidal CO2 and arterial blood pressure closely. Avoid in patients with known or suspected malignant hyperthermia susceptibility. Use a calibrated vaporizer to deliver precise concentrations (1-3% for induction, 0.5-2% for maintenance). |
| Patient Advice | This medication is for hospital use only and will be administered by an anesthesia provider. · You may experience drowsiness, dizziness, or confusion after waking from anesthesia. · Do not drive or operate machinery for at least 24 hours after receiving this drug. · Inform your doctor if you have a personal or family history of malignant hyperthermia. · Report any muscle rigidity, fever, or dark urine to your healthcare provider immediately. |
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