Influence of water on the percutaneous absorption of 2-butoxyethanol in guinea pigs

Anesthetized guinea pigs were exposed for 2 h to aqueous solutions (5-100%, corresponding to 0.38-7.6 mol/l) of 2-butoxyethanol (ethylene glycol monobutyl ether, BE) by epicutaneous administration in a sealed glass ring on the clipped back of the animal. After a recovery period of 2 h, the animals were exposed to undiluted BE in a second glass ring for an additional period of 2 h. Blood samples were obtained via the carotid artery and analyzed for BE by gas chromatography. To reduce the influence of interindividual variation in the kinetics, the dermal uptake rate of BE from the water solutions was expressed relative to that of the undiluted solvent obtained from the second exposure period of the same animal. The relative percutaneous uptake rates were approximately equal from the 5, 10, 20, and 100% solutions of BE, while they were approximately twice as high from the 40 and 80% solutions. The results suggest that water facilitates the percutaneous absorption of BE.