Compound A — FRCA Primary MCQ
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Correct answer: B — It is formed by alkaline degradation of sevoflurane in carbon dioxide absorbent
Compound A, pentafluoroisopropenyl fluoromethyl ether, is formed when sevoflurane undergoes alkaline degradation in carbon dioxide absorbents containing strong bases such as sodium hydroxide or potassium hydroxide. Its circuit concentration increases with higher absorbent temperature, higher sevoflurane concentration and lower fresh gas flow. Hepatic CYP2E1 metabolism instead produces hexafluoroisopropanol, inorganic fluoride and carbon dioxide, so C is incorrect. Compound B is produced downstream when methanol reacts with Compound A, not the reverse. Compound A is not a product of photodegradation in the vaporiser. Thus E describes the relevant mechanism.
Reference: Sevoflurane Baxter, 100%, inhalation vapour, liquid. Summary of Product Characteristics, sections 5.2, 5.3 and 6.2; revised 31 March 2023. https://www.medicines.org.uk/emc/product/1866/smpc