The metabolism of methyl isobtyl ketone and its biological monitoring Part 1. Qualitative and quantitative studies of methyl isobtyl ketone exhaled from the lungs and excreted in the urine, and the metabolites in the urine of rats injected with methyl isobutyl ketone

Rats were injected intraperitoneally with 100mg/kg, 200mg/kg and 300mg/kg of methyl isobutyl ketone (MIBK) in a single dose, and the amount of MIBK in the expired air and in the urine were studied. One of the metabolites was identified as 4-methyl-2-pentanol (4M2P) in the urine by gas chromatography-mass spectrometry. The concentration of MIBK in the exhaled air attainend its maximum within 0.5 hour. Thereafter it decreased with a half life of 0.6 hour, and 41.1±8.7 (m±SD) % of the total amount injected was exhaled within 24 hours. The concentration of MIBK in the urine attained its maximum within 3 hours after injection. Then it decreased with a half life of 1.8 hours and 0.19±0.11 (m±SD) % of the total amount administered was excreted in 18 hours. The concentration of 4M2P in the urine attained its maximum in 3-6 hour and decreased gradually thereafter. Its half life was 3.2 hours and 0.31±0.18 (m±SD) % of the total amount was excreted in 12 hours.

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