Propylene glycol is a synthetic, colorless, odorless, and slightly sweet-tasting liquid that is widely used in medicines, foods, and cosmetics. It acts mainly as a solvent, helping to dissolve active drug ingredients and improve their stability and delivery in formulations such as syrups, injections, creams, and inhalation products. In the body, it is absorbed quickly from the gastrointestinal tract and can also be absorbed through the skin. It is metabolized in the liver into lactic acid and pyruvic acid, which are then further processed through normal metabolic pathways. Most of it is eliminated through the kidneys in urine. At normal exposure levels, it is generally considered safe, but very high doses or prolonged exposure may lead to toxicity such as metabolic disturbances.
USES
Used as a solvent in medicines to dissolve active drug ingredients
Acts as a carrier in oral syrups and liquid formulations
Used in injectable drugs to improve drug stability and solubility
Found in topical creams and ointments to enhance absorption
Used in inhalation and nebulizer solutions in some medical preparations
Common ingredient in cosmetics and personal care products as a humectant (moisture-retaining agent)
Used in the food industry as a stabilizer and preservative (in approved amounts)
SIDE EFFECTS
Nausea or vomiting (at high exposure)
Headache
Dizziness
Mild skin irritation or redness (when applied topically in sensitive individuals)
Allergic reactions (rare, such as rash or itching)
Central nervous system effects like drowsiness or confusion (in high doses)
Metabolic disturbances such as lactic acidosis (rare, usually with excessive or prolonged exposure, especially in vulnerable patients)
TOXICITY
Toxicity is rare at normal doses but can occur with high or prolonged exposure
May cause central nervous system depression (confusion, drowsiness, seizures in severe cases)
Can lead to metabolic acidosis, especially in infants, elderly, or patients with kidney or liver impairment
May cause kidney dysfunction in severe overdose situations
High intravenous doses (from some medications containing it) can accumulate in the body
More likely to cause toxicity when elimination is reduced (e.g., in renal failure)
Usually reversible once exposure is stopped and supportive treatment is given.
