What is a Class 4 Medicines Notification? Understanding MHRA 'Caution in Use' Alerts

October 11, 2025 •

5 min read

The UK's Medicines and Healthcare products Regulatory Agency (MHRA) issues hundreds of safety alerts annually, with a class 4 medicines notification representing the lowest level of risk for a product defect, such as a minor error in packaging or a patient information leaflet. These alerts are crucial for maintaining the integrity of pharmaceutical products and protecting public health.

Quick Summary

A Class 4 medicines notification is a "Caution in Use" alert issued by the UK's MHRA for minor drug defects, like packaging or leaflet issues, that pose no significant patient risk.

Key Points

Low Risk Category: A Class 4 medicines notification is the lowest level of drug alert issued by the UK's MHRA, indicating a minor, non-critical defect.
'Caution in Use': This alert is often referred to as a 'Caution in Use' notice, signifying that while there is an issue, it does not pose a significant threat to patient safety or product efficacy.
Common Defects: Common causes include outdated patient information leaflets (PILs), packaging artwork errors, or minor administrative mistakes like incorrect barcodes.
No Immediate Recall: Unlike Class 1, 2, and 3 recalls, a Class 4 notification does not require the withdrawal of stock from patients or pharmacies.
Healthcare Professionals' Role: Pharmacists and other healthcare providers are responsible for staying informed about these alerts, checking their inventory for affected batches, and providing corrected information to patients where necessary.
Quality Control: These alerts are a vital part of pharmacovigilance, ensuring that even minor discrepancies in pharmaceutical products are addressed to maintain quality and patient confidence.

What is a Class 4 Medicines Notification?

A Class 4 medicines notification is the lowest risk category of drug alert issued by the Medicines and Healthcare products Regulatory Agency (MHRA), the governing body in the UK responsible for ensuring medicines and medical devices are safe and effective. Officially known as a 'Caution in Use' notice, this type of notification is typically triggered by a non-critical defect in a pharmaceutical product. Unlike more serious alerts that require immediate product recall from patients or supply chains, a Class 4 notification focuses on informing healthcare professionals of a minor issue that does not pose a significant threat to patient safety.

These alerts are a vital part of the pharmacovigilance system, which is the practice of monitoring the effects of medical drugs after they have been licensed for use, especially in order to identify and evaluate previously unreported adverse reactions. By promptly communicating even minor issues, the MHRA and pharmaceutical companies can maintain the highest standards of quality control. The defects addressed by a Class 4 notification are usually related to a drug's packaging or printed materials, such as an outdated patient information leaflet (PIL) or a barcode error.

Common Triggers for a Class 4 Notification

Several types of minor manufacturing or quality control errors can lead to the issuance of a Class 4 'Caution in Use' notification. These defects, while not posing a direct health risk, still require attention to prevent potential confusion or medication errors down the line.

Incorrect or outdated Patient Information Leaflet (PIL): A very common reason for a Class 4 notification is when a batch of a medicine contains a PIL that is not the most current version. For example, a leaflet might be missing the latest side effect information or include outdated advice.
Packaging artwork errors: Mistakes on the product's outer packaging, such as an incorrect European Article Number (EAN) barcode, inaccurate dosage instructions, or other typographical errors, are typical Class 4 issues.
Minor stability concerns: In some cases, a minor, non-critical deviation in a product's stability testing that doesn't compromise its efficacy or safety may result in a notification rather than a recall.
Administrative or labelling errors: This can include missing information on a batch label, errors in the expiry date displayed on the box, or other minor administrative problems that don't affect the product itself.

Comparing MHRA Medicines Alert Classes

The MHRA categorizes its alerts based on the severity of the defect and the risk to the patient. Understanding the different classes helps healthcare professionals prioritize and act appropriately. A Class 4 is at the very bottom of this hierarchy, which includes various levels of recall as well as notifications.


Feature	Class 1 Medicines Recall	Class 2 Medicines Recall	Class 3 Medicines Recall	Class 4 Medicines Notification
Severity	Most serious; potentially life-threatening or serious harm.	Significant potential for harm, but not life-threatening.	Unlikely to cause patient harm; non-compliance with authorisation.	Negligible risk to patients; minor defect or error.
Action Required	Urgent action to remove all stock from patients and supply chain.	Removal of affected batch(es) from clinics and pharmacies.	Removal of affected batch(es) from pharmacies, often less urgently.	Caution in use; healthcare professionals informed; no stock removal required.
Example	Contamination with a harmful substance or incorrect active ingredient.	Incorrect dosing information on a label causing potential moderate harm.	Dissolution failure during stability testing that does not pose immediate risk.	Outdated Patient Information Leaflet or minor carton artwork error.
Scope	All affected stock withdrawn immediately.	Specific batch(es) withdrawn from pharmacy and wholesale level.	Specific batch(es) withdrawn from pharmacy and wholesale level.	Specific batch(es) are subject to a cautionary notice.

The Role of Pharmacists and Healthcare Professionals

When a Class 4 notification is issued, the primary responsibility falls on pharmacists and other healthcare professionals. They must be aware of the alert and its implications, even though no immediate patient harm is expected. Handling a Class 4 alert is more about administrative diligence and ensuring long-term patient safety than an urgent recall procedure.

Steps for managing a Class 4 notification include:

Monitor MHRA Alerts: Pharmacists must regularly check the MHRA website for new safety communications, recalls, and notifications, including Class 4 alerts.
Verify Stock: Upon receiving an alert, pharmacy staff should check their inventory for the specific batch numbers and products mentioned in the notification.
Update Records and Advise: If the pharmacy holds or has dispensed the affected product, they should note the issue in their records. While a patient recall isn't necessary, the pharmacist can provide the updated information to the patient during their next visit, particularly if it concerns a leaflet update.
Administrative Action: In cases of labelling errors, such as a barcode issue, the notification might provide instructions on how to handle the administrative problem, though it does not affect the patient's use of the medication.

The Importance of the Class 4 System

While a Class 4 notification may seem like a minor issue, it underscores a commitment to thorough pharmacovigilance and consumer protection. These alerts ensure that even small discrepancies that could potentially cause confusion or diminish patient confidence are addressed promptly. For example, an outdated patient leaflet might not cause harm, but it could lead to unnecessary worry if a patient reads about a missing side effect or a changed dosage instruction. The system prevents these minor issues from escalating into more significant problems over time.

Furthermore, Class 4 alerts form part of a broader regulatory framework that holds manufacturers accountable for the entire lifecycle of their product, from development to market. By issuing these notices, the MHRA maintains a comprehensive log of product issues, allowing for long-term monitoring and trend analysis. This data can inform future manufacturing guidelines and prevent similar, potentially more serious, issues from occurring again.

Conclusion

A class 4 medicines notification is the least severe form of drug alert issued by the UK's MHRA, signaling a 'Caution in Use' situation for a pharmaceutical product. These notices are reserved for minor defects, typically related to packaging or printed materials, that pose no significant risk to patient safety. While not requiring a product recall, these alerts play a crucial role in maintaining quality control and transparency in the pharmaceutical industry. By diligently monitoring and acting upon these notifications, healthcare professionals ensure that patients receive the most accurate information possible and that the highest standards of safety and quality are upheld throughout the medication supply chain.

Visit the official MHRA Drug & Device Alerts page for recent examples and full details.

Frequently Asked Questions

The primary difference lies in the level of risk to the patient. A Class 1 recall is issued for severe, potentially life-threatening risks, requiring immediate product withdrawal. A Class 4 notification is for minor defects that pose no significant risk, and does not require stock removal.

No, a Class 4 notification does not mean the medicine is unsafe. It indicates a minor defect, such as an error on the packaging or in the patient information leaflet, that does not affect the safety or efficacy of the medicine itself.

Pharmacists review the alert to identify affected batch numbers. They may update their records and provide corrected information to patients, such as a corrected patient information leaflet, but do not need to withdraw the product from their shelves.

If a Class 4 alert is issued for a barcode error, the notification serves to inform pharmacies and distributors of the administrative defect. It ensures that the issue does not cause problems with inventory management, but it has no impact on patient safety.

Yes, they are relatively common compared to higher-class recalls. They are part of the routine monitoring process and indicate a proactive approach to quality control, addressing minor issues before they can cause confusion.

The MHRA publishes all drug and device alerts, including Class 4 notifications, on its website. Patients can check this resource or speak with their pharmacist to get information on any potential issues with their medication.

No, the classification systems differ. The UK uses the MHRA system with Class 1-4 for medicines and devices. The US Food and Drug Administration (FDA) uses a different system, classifying recalls as Class I, Class II, or Class III based on health hazard.