Excipient (pharmacologically inactive substance)
What is it?
Propylene glycol (CH8O2) is a commonly used drug solubilizer in topical, oral, and injectable medications. It is used as stabilizer for vitamins, and as a water-miscible cosolvent.[1] Propylene glycol has been used for over 50 years in a large variety of applications. As a pharmaceutical additive, propylene glycol is generally regarded as safe. However, in the pediatric population, propylene glycol has been implicated in toxicity. Cases of hyperosmolality from absorption of creams applied to burns have been reported. Contact dermatitis has also occurred with topical application in the pediatric population. Hemolysis, central nervous system depression, hyperosmolality, and lactic acidosis have been reported after intravenous administration.[2] Propylene glycol is metabolized to lactic acid, which may lead to the reported lactic acidosis.
The high concentration of propylene glycol contained in certain intravenous drug products, such as phenytoin, diazepam, digoxin, and etomidate, may induce thrombophlebitis. Rapid infusion of solutions containing high concentrations of propylene glycol-containing drugs has been linked to respiratory depression, arrhythmias, hypotension, and seizures. Seizures and respiratory depression have also occurred in children who have ingested oral solutions containing propylene glycol.[2]
Propylene glycol is also used as moisturizer in cosmetic products and as a dispersant in fragrances. There are many other food and industrial uses for propylene glycol. As a food additive, propylene glycol is on the U.S. Food and Drug Administration (FDA) generally regarded as safe list (not to be confused with ethylene glycol, which is extremely toxic if ingested). According the FDA, as a food additive, propylene glycol is metabolized in the body and is used as a normal carbohydrate source. Long-term use and substantial quantities of propylene glycol (up to five percent of the total food intake) can be consumed without causing toxicity. There is no evidence in the available information on propylene glycol that demonstrates, or suggests a hazard to the public when they are used at levels that are now current or might reasonably be expected in the future.[3][4]
