Fenchone

Fenchone is a monoterpenoid ketone occurring substantially in Spanish lavender, bitter fennel and thuja oils. Its safety profile shows the compound is relatively benign at standard use levels.

Skin. A 4 percent patch test on human subjects produced neither irritation nor sensitization.

Oral and dermal. Acute oral LD50 in rats is 6.16 g/kg. Acute dermal LD50 in rabbits exceeds 5 g/kg.

Neurology. Subcutaneous injection at 1,133 mg/kg in mice produced convulsions, but not at 500 mg/kg. In a 16-day oral study in dogs, it was convulsant and lethal at 1,400 mg/kg/day, produced transient tremors at 750 mg/kg/day, and had no apparent effects at 210 to 420 mg/kg/day. The very high doses are not representative of therapeutic use.

Mutagenicity. Not mutagenic in Salmonella strains TA97, TA98, TA100 or TA1535. Not genotoxic in rat bone marrow micronucleus tests.

In both dogs and rabbits, fenchone is metabolized by hydroxylation. 4-Hydroxyfenchone and 5-hydroxyfenchone appear in dog urine, while 8-, 9- and 10-hydroxyfenchone appear in rabbit urine.

The French regulation on fenchone in absinthe dates from 1915, a legislative response to what was perceived as absinthe toxicity at the time. It is not based on modern toxicological data.