Usage
Propylene glycol is used as a solvent or humectant in many pharmaceutical preparations, including oral, intravenous, and topical medications, cosmetics, and food products. It is also utilized in some medical procedures, such as during surgery. Propylene Glycol itself doesn’t fit neatly into a single pharmacological classification. Its role is as an excipient, meaning it aids drug delivery and formulation rather than having a specific therapeutic action. It aids in dissolving medications and helps them be absorbed by the body.
Alternate Names
- 1,2-Dihydroxypropane
- 1,2-Propanediol
- Methyl ethyl glycol
- Propane-1,2-diol
- Trimethyl glycol
Brand names vary depending on the formulation.
How It Works
Pharmacodynamics: Propylene glycol primarily acts as a delivery vehicle or humectant with limited direct effects on the body when used within approved limits. At high concentrations or with prolonged use, it can cause hyperosmolality and CNS depression.
Pharmacokinetics:
- Absorption: Propylene glycol is rapidly absorbed following oral administration, with peak plasma concentrations occurring within 1-2 hours. It is also absorbed through the skin.
- Metabolism: Propylene glycol is primarily metabolized in the liver by alcohol dehydrogenase to lactic acid, then to pyruvic acid which enters the citric acid cycle.
- Elimination: Propylene glycol and its metabolites are primarily excreted by the kidneys. A small portion might be eliminated through the lungs or in feces.
Mode of Action (as an excipient): Propylene glycol enhances drug solubility and absorption. As a humectant, it attracts and retains water, aiding in moisture retention in topical formulations. It does not have specific receptor binding, enzyme inhibition, or neurotransmitter modulation properties itself. Elimination primarily occurs via renal excretion after hepatic metabolism. The rate of elimination is influenced by liver and kidney function.
Dosage
Propylene Glycol dosing depends heavily on the specific drug formulation and intended use. It’s not typically prescribed as a standalone medication. The following is based on general guidelines for propylene glycol as an excipient:
Standard Dosage
It is difficult to give a standardized dosage for propylene glycol since its usage is generally tied to other medications as a solvent or excipient.
Adults: Dosage varies considerably according to the specific medication and clinical context.
Children: Use with extreme caution in children under 4, especially neonates and pre-term infants due to the risk of toxicity. Dosages must be carefully calculated based on body weight and the specific drug formulation.
Special Cases:
- Elderly Patients: Exercise caution, especially with impaired renal or hepatic function. Dose adjustments might be necessary.
- Patients with Renal Impairment: Dose reduction is often required.
- Patients with Hepatic Dysfunction: Dose reduction is typically necessary.
- Patients with Comorbid Conditions: Careful monitoring is needed.
Clinical Use Cases
Dosage varies dramatically depending upon the intended application. Consultation with pharmaceutical guidelines related to the particular medication being used is essential.
Dosage Adjustments
Adjustments are based on renal and hepatic function, age, and concomitant medications. Serum levels monitoring may be useful in some cases.
Side Effects
Common Side Effects
- Skin irritation (with topical use)
- Nausea and vomiting
- Headache
Rare but Serious Side Effects
- Lactic acidosis
- Seizures
- Hyperosmolality
- CNS depression
- Cardiac arrhythmias (rare)
- Renal toxicity (high doses or prolonged use)
Long-Term Effects
Limited data is available on truly long-term effects. Kidney function should be monitored with chronic high dose use.
Adverse Drug Reactions (ADR)
Serious ADRs like lactic acidosis, seizures, and acute renal failure demand immediate discontinuation and supportive care.
Contraindications
- Known hypersensitivity to propylene glycol
- Infants and children younger than 4 years old
- Pregnant and breastfeeding women (use with caution and only if clearly necessary)
- Patients with severe renal or hepatic impairment
Drug Interactions
- Alcohol (ethanol) – Co-administration can exacerbate CNS depressant effects.
- Drugs metabolized by alcohol dehydrogenase – Propylene glycol may inhibit the metabolism of these medications.
- Certain medications (e.g., disulfiram, metronidazole) are contraindicated with propylene glycol due to potential increased toxicity.
- Interaction with PEG-conjugated medications: Reduced efficacy of some PEG medications has been reported.
Pregnancy and Breastfeeding
Propylene glycol is considered Pregnancy Category C. It can cross the placenta and is present in breastmilk. Use only if the potential benefits outweigh the potential risks to the fetus or nursing infant.
Drug Profile Summary
- Mechanism of Action: Enhances drug solubility, delivery and moisture retention (as an excipient).
- Side Effects: Skin irritation, nausea, vomiting, headache (common); lactic acidosis, seizures, hyperosmolality (rare but serious).
- Contraindications: Hypersensitivity, infants and young children, severe hepatic or renal impairment, pregnancy and breastfeeding (caution).
- Drug Interactions: Alcohol, drugs metabolized by alcohol dehydrogenase, disulfiram, metronidazole, some PEG-conjugated medications.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: Varies widely based on the formulation and route of administration; consult specific drug guidelines.
- Monitoring Parameters: Renal function (with long-term or high dose use), serum osmolality and lactate levels.
Popular Combinations
Propylene glycol is commonly found in combination with various medications for different applications. No specific combinations are universally popular across all clinical scenarios. Always check the composition of the specific product used.
Precautions
- Pre-screening for allergies is advisable, particularly for topical applications.
- Caution is necessary in patients with pre-existing renal or hepatic impairment.
- Monitor for signs of toxicity, especially with high doses.
- Avoid in children under 4 years.
- Careful consideration needed during pregnancy and breastfeeding.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Propylene Glycol?
A: Propylene glycol dosage varies widely depending on the specific medication and route of administration. Consult product-specific guidelines. It’s not prescribed independently.
Q2: What are the common side effects of Propylene Glycol?
A: Common side effects may include skin irritation (topical use), nausea, vomiting, and headache.
Q3: Is Propylene Glycol safe for pregnant or breastfeeding women?
A: Propylene glycol is a Pregnancy Category C drug, so it should be used cautiously and only when potential benefit outweighs the potential risk to the fetus. It is present in breast milk, so caution is advised during breastfeeding.
A: Primarily in the liver by alcohol dehydrogenase to lactic acid and further broken down.
Q5: What are the contraindications for Propylene Glycol use?
A: Hypersensitivity to propylene glycol, infants and young children (under 4 years), severe renal or hepatic dysfunction. Pregnant and breastfeeding women should use it cautiously.
Q6: Can Propylene Glycol interact with alcohol?
A: Yes, concomitant use of propylene glycol and alcohol can increase CNS depression.
Q7: How should Propylene Glycol toxicity be managed?
A: Treatment of propylene glycol toxicity focuses on supportive care, which may include managing hyperosmolality, acidosis, and seizures. Hemodialysis might be necessary in severe cases.
A: Propylene glycol acts primarily as a solvent and humectant, enhancing drug delivery and stability. It helps to dissolve medications and increase their absorption.
Q9: How should Propylene Glycol be administered?
A: The administration route (oral, topical, intravenous) depends on the specific drug formulation. Always refer to the product’s guidelines.
Q10: What are the signs of Propylene Glycol toxicity?
A: Signs and symptoms can include CNS depression, hyperosmolality, lactic acidosis, seizures, cardiac arrhythmias, and acute renal failure.
