Dosing and uses of Forane (isoflurane)
Adult dosage forms and strengths
inhalation solution
- 100mL
- 250mL
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
Pediatric dosage forms and strengths
Safety & efficacy not established
Forane (isoflurane) adverse (side) 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)
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
Pregnancy and lactation
Pregnancy category: C
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.
Pharmacology of Forane (isoflurane)
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)
