Studies of isopropyl myristate show that it has a very low degree of irritability and exhibits no sensitizing propensities in animals following topical and parenteral administration. It is nontoxic to animals, and well tolerated following injections of moderate amounts. Its mixture with aluminum monostearate in 2 per cent solution of the latter compound retains effective therapeutic concentrations of penicillin (procaine enicillin) for periods up to forty-eight hours after intramuscular injection in rabkts. In experiments on ovariectomized rats it compared favorably with sesame oil as a repository vehicle for estrogens.
SOPROPYL MYRISTATE is a clear, colorless, virtually odorless liquid (1). We have determined that it forms a thixotropic mixture with 10% beeswax but not with amounts of beeswax less than 10%. It is oil miscible, water immiscible, stable and not susceptible to rancidity; it is reported to have good solvent powers, a low order of sensitization when applied to the skin of humans, and a low toxicity when administered topically and orally to rabbits and rats, respectively (1). I n recent years, isopropyl myristate because of its properties is being widely used as a substitute for vegetable oils in many cosmetic (2) and pharmaceutical preparations (3). Due to the physical similarity of isopropyl myristate to many of the vegetable oils now being used as repository vehicles, an investigation was made to determine if this compound might also be adapted to such use. Experiments were conducted to determine its toxicity, usefulness as a vehicle, and the extent of irritative effects. Animals were also tested to determine their sensitivity to this compound. The effects of isopropyl myristate on prolonging the therapeutic concentration of penicillin in the blood were studied in rabbits. Ovariectomized rats were employed in the studies of the adaptability of the compound for estrogenic repository administration.
EXPERIMENTAL
Acute Toxicity.-Due to the nontoxic effects of large amounts of isopropyl myristate administered orally to rats as reported elsewhere (l), it was felt that similar amounts should be administered intraperitoneally to mice to determine the acute toxicity by this route of administration. Male Swiss strain albino mice weighing 18 f 1 Gm. were used. The