Isoflurane

FORANE

What it isVolatile GABA-A modulator, NMDA antagonist, and HCN-1 blocker; maintenance of anesthesia.

Why this oneLow cost and potent maintenance anesthesia keep it widely used where rapid emergence is less important.

What limits itPungency limits induction. It can trigger malignant hyperthermia and has substantial environmental persistence.

FDA-approved for

FDA dosing	Population	Start	Target	Max
Induction of general anesthesia	Adults	1.5-3% inspired (surgical anesthesia in 7-10 min)
Maintenance of general anesthesia	Adults	1-2.5% with N2O (add 0.5-1% with O2 alone)

Renal Undefined

Hepatic Contraindicated after prior halogenated-anesthetic hepatitis/unexplained hepatic dysfunction; use with caution in hepatic disease

Administer only by personnel trained in general anesthesia, via a vaporizer designed for isoflurane
Individualize and titrate to effect by age and clinical status (MAC decreases with increasing age)
Replace desiccated CO2 absorbent before use to avoid carbon monoxide formation
Have airway, ventilation, oxygen, and circulatory resuscitation immediately available

Patients in whom general anesthesia is contraindicated
Known or suspected genetic susceptibility to malignant hyperthermia
History of confirmed hepatitis or unexplained moderate-severe hepatic dysfunction after a halogenated inhalational anesthetic

Malignant hyperthermia — discontinue triggers, give IV dantrolene, supportive care
Perioperative hyperkalemia — especially neuromuscular disease/Duchenne muscular dystrophy
Hepatic reactions/sensitivity hepatitis with repeated exposure
Hypersensitivity reactions, incl. anaphylaxis
QT prolongation/torsade de pointes — monitor susceptible patients
Carbon monoxide from desiccated CO2 absorbents
Pediatric neurotoxicity with >3 h exposure in children <3 yr
Dose-dependent hypotension/reduced systemic vascular resistance

Pregnancy No adequate human studies; animal embryofetal toxicity; prolonged 3rd-trimester/early-life exposure raises neurotoxicity concern.

Lactation Insufficient data on excretion in human milk; weigh risks and benefits before use in nursing women.

NO BOXED WARNINGS

Principal riskMalignant hyperthermia trigger; pungency limits induction

Direct muscarinic antagonism0 / 4