Propylene Glycol

Abstract

The increasing use of propylene glycol as a solvent for various pharmaceutical preparations 1 and coloring extracts, 2 and its possible use as a food, indicates the need for a better understanding of the actions of this alcohol. The known production of oxalic acid in the metabolism of ethylene glycol 3 , 4 has been responsible for the substitution of propylene glycol for the former, since oxalic acid is not a possible metabolite of the latter. 5 The properties, general actions, and acute and chronic toxicities of propylene glycol have been investigated by Seidenfeld and Hanzlik 5 ; toxicity was unusually low.

The concentration of propylene glycol in the blood was determined by treating the protein-free filtrate with a solution of potassium dichrornate in strong sulphuric acid, and estimating the amount of reduced dichromate iodometrically. From this value was subtracted the amount of oxidizable material normally present in the blood, a variable which remains relatively constant in fasting animals. In urine, the glycol was estimated directly by using an aliquot portion of a 1:100 dilution, and subtracting the blank value for normal urine from the final result.

The concentration of propylene glycol in the bloods of 2 dogs and 10 rabbits was followed for variable periods after giving doses from 1 to 12 cc. per kilogram body weight, intravenously or orally; the dogs were used repeatedly.

Figure 1 shows the rate of disappearance of propylene glycol from the blood of dogs following the administration of 2 cc. and 4 cc. per kilo intravenously, and 8 cc. gastrically; the intravenous doses are compared with similar doses of ethyl alcohol.

The rate of disappearance of propylene glycol from the blood is proportional to its concentration in the body, as contrasted with alcohol, which disappears at a constant rate 6 .