Which inhalant is associated with tissue retention up to 50% and metabolism for elimination?

• A. Nitrous oxide
• B. Sevoflurane
• C. Methoxyflurane
• D. Desflurane

Answer: (C)

Tissue solubility and metabolic clearance determine how an inhaled anesthetic leaves the body. Methoxyflurane is known for very high lipid solubility, so it is stored in tissues and fat, leading to substantial tissue retention—reported to be up to about half of the inhaled amount. Because a large portion is also metabolized by the liver to fluoride-containing metabolites, elimination relies significantly on metabolic processes rather than just being breathed out. This combination—long tissue storage and substantial hepatic metabolism for clearance—sets methoxyflurane apart from other inhalants, which are cleared mainly by exhalation with minimal metabolism.