Propylene Glycol in Paediatric Oral Suspensions: An Excipient Risk Assessment Your Quality Unit Can Defend

Introduction

In July 2026, Health Canada published a safety brief in its Health Product InfoWatch that should make every quality unit and regulatory affairs team pause. The brief warns that carbamazepine and oxcarbazepine oral suspensions, two common anti-seizure medicines, can expose very young children to harmful amounts of propylene glycol, an excipient most people never think about. Propylene glycol is not the active ingredient. It is a solvent and carrier, listed among the non-medicinal ingredients. Yet in neonates and young children it can accumulate to the point of metabolic acidosis, acute kidney injury and liver dysfunction.

This is not a Canada-only signal. The European Medicines Agency maintains a dedicated questions-and-answers document on propylene glycol used as an excipient, and in late 2025 and 2026 regulators in the United Kingdom and Italy issued their own communications about propylene glycol in carbamazepine liquid. When several trusted regulators move on the same excipient in the same window, it is a clear instruction to companies: your excipient risk assessment for paediatric use needs to be current, documented and defensible.

This article explains what Health Canada said, why propylene glycol behaves differently in the very young, and the practical steps a market authorization holder, manufacturer or importer should take. It is written for regulatory and quality leaders at pharmaceutical and natural health product companies who need an excipient risk assessment that will hold up under inspection.

Executive Summary

Propylene glycol is generally safe in adults at the levels used in medicines. The problem is developmental. Newborns and very young children clear propylene glycol slowly because the enzyme and kidney pathways that remove it are still maturing. A dose that is harmless in an adult can accumulate in a neonate. Because these suspensions are sometimes used off-label in young children when no suitable alternative exists, the exposure question lands squarely with prescribers, pharmacists and the companies that hold the product authorizations.

What Health Canada's July 2026 Safety Brief Actually Says

In short: Health Canada warned that carbamazepine and oxcarbazepine oral suspensions, authorized only for patients 6 years and older, may cause propylene glycol accumulation and toxicity when used off-label in neonates and young children, because these patients clear propylene glycol poorly. It set age-based exposure thresholds and asked prescribers to avoid these products in neonates and to use them in young children only when no suitable alternative therapy exists.

The brief is a clinical safety communication aimed primarily at health professionals, but it carries direct consequences for regulatory and quality teams. It names propylene glycol as the hazard, identifies the populations at risk, and sets quantitative thresholds. For a market authorization holder, each of those elements maps to an action: a hazard to assess, a population to address in labelling, and a numerical limit against which to measure your product's contribution.

Health Canada's thresholds are summarized below. They are the same order of magnitude used internationally, which is why your risk assessment can draw on both Canadian and European reference points.

Health Canada's recommendations are practical. Avoid propylene glycol-containing products in neonates. In young children, use them only when no suitable alternative therapy exists and when expected benefits outweigh the risks. Monitor closely, including osmolarity and anion gap testing where clinically appropriate. Check product monographs for propylene glycol among the non-medicinal ingredients, because other medicines and combined low-dose products can add to total exposure. Report suspected adverse reactions to the Canada Vigilance Program. Possible complications named in the brief are metabolic acidosis, acute kidney injury and liver dysfunction.

Why Propylene Glycol Is a Hidden Risk in the Very Young

In short: Newborns and very young children metabolize and excrete propylene glycol far more slowly than adults because the liver enzyme alcohol dehydrogenase and kidney clearance pathways are still immature. Propylene glycol that an adult would clear in hours can accumulate in a neonate, raising blood osmolarity and the anion gap and, in severe cases, causing metabolic acidosis, kidney injury and liver dysfunction.

Propylene glycol is one of the most widely used solvents in liquid and some semi-solid medicines. It dissolves active ingredients that water alone cannot carry, which is why it appears so often in oral suspensions, oral solutions and some injectables. In adults, the body breaks it down through alcohol dehydrogenase into lactic and pyruvic acid, then clears the remainder through the kidneys. Both pathways are underdeveloped in neonates. The result is a longer half-life and a tendency to accumulate with repeated doses.

This is why the hazard is developmental rather than a simple matter of dose per kilogram. A single exposure may be tolerated, but anti-seizure medicines are taken regularly, often several times a day, sometimes for years. Repeated dosing in a patient who cannot clear the excipient is the scenario that turns a routine formulation into a safety signal. It is also why cumulative exposure, not just the dose from one product, is the number that matters.

The clinical consequences are serious. Metabolic acidosis disturbs the body's acid-base balance. Acute kidney injury can impair the very organ responsible for clearing the excipient, creating a feedback loop. Liver dysfunction affects the enzyme pathway that metabolizes propylene glycol in the first place. None of these outcomes is common at authorized doses in the authorized age group, but all become plausible when a product designed for a 6-year-old is given to a 3-week-old.

What This Means for Your Quality Unit and Regulatory File

In short: Treat propylene glycol as a product-specific hazard that requires a documented excipient risk assessment. Quantify the propylene glycol your product delivers at the dose and frequency used, compare it against the Canadian and international thresholds, confirm your product monograph and labelling disclose the excipient and its paediatric cautions, and make sure your pharmacovigilance system is primed to detect and report related adverse events.

Inspectors do not expect you to reformulate overnight. They expect evidence that you understood the risk, assessed it against current science, and took proportionate action. A quality management system that can produce a dated, signed excipient risk assessment on request is in a far stronger position than one that treats non-medicinal ingredients as an afterthought. This is the difference between a defensible file and an observation.

Build an excipient risk assessment that follows ICH Q9 logic

Quality risk management under ICH Q9 gives you the structure. Identify the hazard (propylene glycol accumulation in neonates and young children). Analyze it by quantifying the propylene glycol content per millilitre, the typical and maximum paediatric dose, and the resulting mg/kg/day exposure. Evaluate it against the Health Canada thresholds of 1 mg/kg/day for neonates and 50 mg/kg/day for children 1 month to 5 years. Then control it through labelling, prescriber communication, and, where justified, a reformulation or line-extension project. Document each step and keep the record under change control.

A simple worked calculation belongs in the file. State the propylene glycol concentration in the formulation, multiply by the volume delivered at the relevant dose, divide by the child's weight, and compare the result against the threshold. Where the number crosses the line, record the clinical context (off-label use, absence of alternatives) and the risk control you have chosen. This calculation is exactly what an assessor will ask to see.

Align the product monograph and labelling

Canadian product monographs list non-medicinal ingredients, so propylene glycol should already appear in your monograph. The action now is to confirm the monograph's safety information reflects the current signal: the authorized age range, the paediatric caution, and the advice to avoid use in neonates. Labelling changes are a controlled activity. If you are a drug identification number holder, treat any monograph safety update the way you would any other change, with proper documentation and notification, consistent with Health Canada's summary reports and change-management expectations. For pediatric products more broadly, the review and labelling expectations have been tightening, as our analysis of the 180-day pediatric drug review and the ADHD stimulant monograph changes for children under 6 both show.

Which Products Carry Propylene Glycol and How to Find It

In short: Propylene glycol can appear in any liquid or semi-solid medicine as a solvent or carrier. To find it, read the non-medicinal ingredients section of each product monograph, search the Drug Product Database, and then add up exposure across every propylene glycol-containing product a patient may receive at once, because combined low-dose products can push a child over the threshold even when no single product does.

The trap is cumulative exposure. A child on an anti-seizure suspension may also receive another liquid medicine that contains propylene glycol. Each product on its own might look acceptable, but the total can exceed 50 mg/kg/day. Your assessment should consider the realistic co-medication scenario for the population your product serves, not just the product in isolation.

Use the Drug Product Database to confirm non-medicinal ingredients and authorized indications, and keep a living list of the propylene glycol-containing products in your own portfolio. This is the same discipline that protects you in a recall or a safety review, as our look at how Canada classifies recalls explains.

Reporting and Pharmacovigilance Obligations

In short: Suspected adverse reactions linked to propylene glycol should be reported to the Canada Vigilance Program. Hospitals and healthcare institutions have mandatory reporting duties for serious adverse drug reactions under Vanessa's Law, and market authorization holders must detect, assess and report safety signals and keep their benefit-risk evaluation current.

Health Canada asked health professionals to report suspected adverse reactions to the Canada Vigilance Program. For companies, the obligation runs deeper. A safety brief like this one is a signal input. Your pharmacovigilance system should capture related events, assess whether they change your benefit-risk balance, and document the conclusion. Hospitals already carry mandatory reporting duties for serious adverse drug reactions and medical device incidents under Vanessa's Law, which means more structured data is reaching Health Canada than ever before. Expect excipient-related events in young children to be visible, and be ready to respond.

A documented safety review is also a familiar discipline. When Health Canada completed its summary safety review on ashwagandha and liver injury, licence holders that had already mapped their hazard and evidence were able to respond quickly. The same readiness applies here: the companies that can show a current propylene glycol assessment will manage this signal with far less friction.

Propylene Glycol Compliance Checklist

Use this checklist to confirm your excipient risk assessment is current and defensible:

• Confirm whether each liquid or semi-solid product in your portfolio contains propylene glycol, and record the concentration per millilitre.
• Calculate the propylene glycol exposure in mg/kg/day at typical and maximum paediatric doses for each relevant product.
• Compare the result against Health Canada's thresholds: 1 mg/kg/day for neonates and 50 mg/kg/day for children 1 month to 5 years.
• Assess cumulative exposure across all propylene glycol-containing products a patient may receive together.
• Verify the product monograph lists propylene glycol among non-medicinal ingredients and reflects the current paediatric caution and authorized age range.
• Document the excipient risk assessment under ICH Q9 logic, dated and signed, and place it under change control.
• Confirm labelling and any safety updates follow your change-management and notification procedures.
• Ensure the pharmacovigilance system is set to detect, assess and report propylene glycol-related adverse events to the Canada Vigilance Program.
• Decide, and record, whether a lower-propylene-glycol or propylene-glycol-free formulation is justified.
• Keep a living list of propylene glycol-containing products for use in recalls, safety reviews and inspections.

Common Mistakes Companies Make

• Treating non-medicinal ingredients as inert. Excipients carry real safety profiles, and propylene glycol in the very young is a clear example.
• Assessing one product in isolation. The threshold is about cumulative exposure, so a single-product view understates the risk.
• Relying on the authorized age range alone. Off-label use in neonates and young children is foreseeable, and regulators expect you to address it.
• Leaving the risk assessment undocumented. An assessment that lives only in someone's head is worthless in an inspection.
• Updating labelling without change control. Safety-driven monograph changes still require proper documentation and notification.
• Failing to connect the safety signal to pharmacovigilance. A brief like this should trigger a signal-management step, not sit unread.

Frequently Asked Questions

Is propylene glycol dangerous in medicines?

Propylene glycol is generally safe in adults at the levels used in medicines and is a very common solvent. The concern is specific to neonates and young children, whose immature liver and kidney pathways clear it slowly, allowing it to accumulate. The risk is about population and cumulative dose, not the excipient being unsafe in general.

Why did Health Canada single out carbamazepine and oxcarbazepine suspensions?

Both are anti-seizure oral suspensions authorized for patients 6 years and older, and both can contain propylene glycol. They are sometimes used off-label in younger children when no suitable alternative exists, and they are taken repeatedly, which is the scenario most likely to cause accumulation in a patient who cannot clear the excipient.

What are Health Canada's propylene glycol exposure limits?

Health Canada's July 2026 brief flags rising risk in term neonates under 4 weeks and preterm neonates under 44 weeks post-menstrual age above 1 mg/kg/day, and in children 1 month to 5 years at cumulative exposure of 50 mg/kg/day or more. Typical neonatal doses of these suspensions can exceed the neonatal threshold.

What should a market authorization holder do now?

Build or refresh a documented excipient risk assessment, quantify the propylene glycol your product delivers, compare it against the thresholds, confirm your product monograph and labelling reflect the paediatric caution, account for cumulative exposure, and make sure your pharmacovigilance system can detect and report related events.

Is this only a Canadian issue?

No. The European Medicines Agency maintains a questions-and-answers document on propylene glycol as an excipient, and regulators in the United Kingdom and Italy have issued communications about propylene glycol in carbamazepine liquid. It is an international signal, which is why a current, well-documented assessment matters across markets.

Do we have to reformulate to remove propylene glycol?

Not automatically. Reformulation is one control option, but regulators expect a proportionate, documented response. For many products the right answer is accurate labelling, prescriber communication and cumulative-exposure guidance. A reformulation or line extension is justified where the risk assessment shows it is warranted.

How MFLRC Can Help

Excipient safety is exactly the kind of quiet, technical risk that separates a defensible quality file from an inspection finding. MFLRC helps pharmaceutical and natural health product companies turn a safety brief like this one into a documented, auditable response. Our quality assurance services build and refresh excipient risk assessments under ICH Q9 logic, structure the supporting calculations, and place them under change control. Our regulatory affairs and licensing team aligns product monographs, labelling and safety notifications with Health Canada's expectations, and our audit and inspection-readiness services stress-test the file before an inspector does.

Whether you need a single excipient risk assessment, a portfolio-wide review of propylene glycol exposure, SOPs for signal management, or a mock audit of your paediatric labelling controls, we provide senior-led, practical support tailored to your products and markets.

Conclusion

Propylene glycol has been in medicines for decades, which is precisely why it is easy to overlook. Health Canada's July 2026 brief is a reminder that an excipient considered routine in adults can be a real hazard in the very young, and that the responsibility for assessing and communicating that hazard sits with the companies that hold the authorizations. The science is settled enough to act on, the thresholds are published, and several regulators are moving in step.

The companies that come through this well will be the ones that already treat excipients as part of their safety profile, keep a current and documented risk assessment, and connect a safety signal to concrete actions in labelling and pharmacovigilance. That is not a reaction to one brief. It is a quality system working the way it should.

Sources and References

• Health Canada, Health Product InfoWatch, July 2026 (propylene glycol safety brief; dutasteride labelling; Ministerial Reliance Order)
• European Medicines Agency, Questions and answers on propylene glycol used as an excipient in medicinal products for human use
• Health Canada, Canada Vigilance Program and adverse reaction reporting
• Health Canada, Drug Product Database
• ICH, Quality guidelines (ICH Q9 Quality Risk Management)