Functional Category
Emollient; oleaginous vehicle; skin penetrant; solvent.
Applications in Pharmaceutical Formulation
Isopropyl myristate is a nongreasy emollient that is absorbed readily by the skin. It is used as a component of semisolid bases and as a solvent for many substances applied topically. Applications in topical pharmaceutical and cosmetic formulations include bath oils; make-up; hair and nail care products; creams; lotions; lip products; shaving products; skin lubricants; deodorants; otic suspensions; and vaginal creams; see Table I. For example, isopropyl myristate is a self-emulsifying component of a proposed cold cream formula,(1) which is suitable for use as a vehicle for drugs or dermatological actives; it is also used cosmetically in stable mixtures of water and glycerol.(2) Isopropyl myristate is used as a penetration enhancer for transdermal formulations, and has been used in conjunction with therapeutic ultrasound and iontophoresis.(3) It has been used in a water-oil gel prolonged-release emulsion and in various microemulsions. Such microemulsions may increase bioavailability in topical and transdermal applications.(4) Isopropyl myristate has also been used in microspheres, and significantly increased the release of drug from etoposide-loaded microspheres.(5) Isopropyl myristate is used in soft adhesives for pressuresensitive adhesive tapes.(6)
Description
Isopropyl myristate is a clear, colorless, practically odorless liquid of low viscosity that congeals at about 58C. It consists of esters of propan-2-ol and saturated high molecular weight fatty acids, principally myristic acid.
Stability and Storage Conditions
Isopropyl myristate is resistant to oxidation and hydrolysis, and does not become rancid. It should be stored in a well-closed container in a cool, dry place and protected from light.
Incompatibilities
When isopropyl myristate comes into contact with rubber, there is a drop in viscosity with concomitant swelling and partial dissolution of the rubber; contact with plastics, e.g. nylon and polyethylene, results in swelling. Isopropyl myristate is incompatible with hard paraffin, producing a granular mixture. It is also incompatible with strong oxidizing agents.
Safety
Isopropyl myristate is widely used in cosmetics and topical pharmaceutical formulations, and is generally regarded as a nontoxic and nonirritant material.(7–9) LD50 (mouse, oral): 49.7 g/kg(10) LD50 (rabbit, skin): 5 g/kg