isoflurane (Rx)

Brand and Other Names:Forane
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

inhalation solution

  • 100mL
  • 250mL
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Anesthesia Induction & Maintenance

Use calibrated vaporizer

Induction: 1.5-3% can produce surgical anesthesia in 7-10 minutes

Maintenance: 1-2.5% with nitrous oxide

Additional 0.5-1% may be needed if given with oxygen alone

Safety & efficacy not established

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Interactions

Interaction Checker

and isoflurane

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    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            1-10%

            Nausea

            Vomiting

            Shivering

            <1%

            Dose-dependent hypotension

            Arrhythmias

            Malignant hyperthermia (rare)

            Elevations in white blood count

            May decrease creatinine and increase BUN

            Ileus, severe (fatal)

            Hepatic dysfunction (postoperative period) (rare)

            Respiratory depression may occur (rare)

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            Warnings

            Contraindications

            Hypersensitivity to isoflurane & halogenated agents

            Genetic susceptibility to malignant hyperthermia

            Cautions

            Caution in coronary heart disease

            May decrease renal and hepatic blood flow

            Postoperative hepatic dysfunction and hepatitis reported

            Rare risk of perioperative hyperkalemia & malignant hyperthermia

            Adequate data have not been developed to establish its application in obstetrical anesthesia

            Should not be used as a sole agent of induction in patients with ventricular dysfunction

            Perioperative Hyperkalemia

            • Inhaled anesthetics associated with rare increases in serum potassium levels that have resulted in cardiac arrhythmias and death in pediatric patients postoperatively  
            • Patients with latent as well as overt neuromuscular disease, particularly Duchenne muscular dystrophy, appear to be most vulnerable
            • Concomitant use of succinylcholine has been associated with most, but not all, of these cases
            • Elevated serum creatinine kinase levels and, in some cases, changes in urine consistent with myoglobinuria observed  
            • Despite similar presentation to malignant hyperthermia, none of affected patients exhibited signs or symptoms of muscle rigidity or hypermetabolic state  
            • Early and aggressive intervention to treat hyperkalemia and resistant arrhythmias recommended  
            • Evaluation for latent neuromuscular disease recomended

            General anesthetics and sedation drugs in young children and pregnant women

            • Brain development
              • Prolonged or repeated exposure may result in negative effects on fetal or young children’s brain development
              • Caution with use during surgeries or procedures in children younger than 3 yr or in pregnant women during their third trimester
              • Assess the risk:benefit ratio in these populations, especially for prolonged procedures (ie, >3 hr) or multiple procedures
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            Pregnancy & Lactation

            Pregnancy

            There are no adequate and well-controlled studies in pregnant women; in animal reproduction studies, embryofetal toxicity was noted in pregnant mice exposed to 0.075% (increased post implantation losses) and 0.3% isoflurane (increased post implantation losses and decreased live- birth index) during organogenesis

            Lactation

            Use caution

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Volatile liquid inhalation anesthetic

            Pharmacokinetics

            Onset: Rapid (7-10 min)

            Duration: Short (depends on blood concentration)

            Minimum Alveolar Conc: 1.3%

            Metabolism: Liver (0.2%)

            Pharmacogenomics

            Increased incidence of malignant hyperthermia with use of volatile anesthetics or depolarizing neuromuscular blockers in patients with gene mutations in ryanodine receptor (RYR1) or calcium channel alpha (1S)- subunit gene (CACNA1S)

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            Formulary

            FormularyPatient Discounts

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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
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            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
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            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
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            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.