Pharmacy Beyond-Use Dating (BUD) Explained Simply

Beyond-Use Dating in Pharmacy Compounding

Beyond-use dating (BUD) is a critical concept in pharmacy compounding that determines how long a compounded preparation can be used after it has been made. Unlike manufacturer expiration dates on commercially available products, beyond-use dates are assigned by the pharmacy based on established guidelines. Understanding BUD is essential for patient safety and is frequently tested on the PTCB exam.

Beyond-Use Date vs. Expiration Date

It is important to distinguish between beyond-use dates and expiration dates. An expiration date is determined by the manufacturer based on stability testing data and appears on commercially produced medications. It indicates the last date the manufacturer guarantees the product meets its labeled specifications.

A beyond-use date is the date after which a compounded preparation should not be used. It is assigned by the compounding pharmacy based on USP guidelines, the nature of the ingredients, the dosage form, storage conditions, and any available stability data. BUD is generally much shorter than a manufacturer's expiration date because compounded preparations have not undergone the same rigorous stability testing.

USP 795 Beyond-Use Dating Guidelines

USP Chapter 795 provides the framework for assigning beyond-use dates to non-sterile compounded preparations. The updated guidelines categorize preparations based on their composition and available stability data:

For preparations compounded from commercially available products where the manufacturer's expiration date is known, the BUD should not exceed the earlier of 25% of the remaining expiration date or six months, unless stability data supports a longer date.

When stability data is not available, USP 795 provides default BUD guidelines based on the type of preparation:

• Non-aqueous formulations (ointments, creams without water, powders): BUD of up to 180 days
• Water-containing oral formulations (solutions, suspensions, syrups): BUD of up to 14 days
• Water-containing topical formulations: BUD based on stability considerations, typically shorter than non-aqueous preparations

These are default guidelines that apply when no specific stability data exists for the preparation. If published stability studies or pharmacy-conducted testing supports a longer BUD, that data may be used instead.

Factors Affecting Beyond-Use Dating

Several factors influence the appropriate beyond-use date for a compounded preparation:

Water activity is one of the most important factors. Water supports microbial growth and can accelerate chemical degradation. Preparations containing water generally receive shorter BUDs than anhydrous (water-free) preparations. This is why aqueous oral preparations are typically limited to 14 days without specific stability data.

Storage conditions directly impact stability. Refrigeration can extend the BUD for many preparations by slowing chemical reactions and inhibiting microbial growth. The assigned BUD should always specify the required storage temperature. Heat, light, and humidity can all accelerate degradation.

Container type affects stability as well. Light-sensitive compounds should be stored in amber containers. Tight-fitting closures prevent moisture absorption and evaporation. The choice of container material (glass vs. plastic) can also matter for certain active ingredients.

Chemical stability of active ingredients varies widely. Some drugs are inherently unstable and degrade quickly once removed from their original formulation. Others are highly stable in compounded preparations. Knowledge of individual drug stability characteristics helps pharmacists assign appropriate BUDs.

Preservatives and Beyond-Use Dating

Preservatives play an important role in extending the beyond-use date of water-containing preparations. Common preservatives used in compounding include methylparaben, propylparaben, benzalkonium chloride, and benzoic acid. When a preparation contains an effective preservative system, it may receive a longer BUD than an unpreserved preparation of the same type.

However, the presence of a preservative does not automatically guarantee a longer BUD. The preservative must be effective at the concentration used and must be compatible with all other ingredients in the formulation.

Documentation Requirements

Every compounded preparation must have its beyond-use date documented on the label and in the compounding record. The label should clearly state the BUD and the required storage conditions. The compounding log should record the basis for the assigned BUD, whether it is based on USP default guidelines or specific stability data.

USP 797 and Sterile Compounding BUD

While this article focuses on non-sterile compounding, it is worth noting that sterile preparations (covered under USP 797) have their own separate BUD guidelines that are generally more restrictive. Sterile BUDs depend on the risk level of compounding and whether the preparation is tested for sterility. Pharmacy technicians working in sterile compounding environments should be familiar with both USP 795 and USP 797 guidelines.

PTCB Exam Tips

For the PTCB exam, remember the key default BUDs from USP 795, understand the difference between expiration dates and beyond-use dates, and know which factors shorten or extend a preparation's BUD. Questions may present a scenario and ask you to determine the appropriate beyond-use date based on the preparation type and available information. Practice these scenarios before exam day.