Propylene glycol used as an excipient

Based on the information provided, here is a summary of the findings related to propylene glycol:

1. Propylene glycol is used as an excipient (inactive ingredient) in pharmaceutical formulations.
2. In safety pharmacology and toxicity studies, signs of ocular and nasal irritation were observed in rats, rabbits, and dogs after exposure to propylene glycol.
3. In clinical studies, propylene glycol concentration did not differ between patients with normal or impaired renal function.
4. a case study in a patient with respiratory failure showed that lorazepam infusion with escalating rates over 5 days resulted in a total propylene glycol load of 540 g, which was associated with mitochondrial activity or altered protein synthesis rate.
5. Repeat-dose toxicity studies in mice found minimally elevated transaminase levels (aLT/aST) in 2/5 male mice, but no histopathology correlate. The no-observed-adverse-effect level (NOaEL) was determined to be 1000 mg/kg.
6. Several predictive animal tests failed to detect any sensitizing properties of propylene glycol.
7. Despite the potential for irritation and rare cases of adverse effects, the low frequency of positive reactions to propylene glycol in the population, given the high level of exposure, suggests a good safety profile for this excipient.

“Propylene Glycol Used as an Excipient.” European Medicines agency Committee for human Medicinal Products (ChMP), October 9, 2017.