The Clock Starts in the Base: How Compounding Bases Set Beyond Use Dates
Every compounded preparation carries a date after which it should not be used, and that date is decided largely by the base it is made in. This guide explains how the date is set, which bases allow up to 180 days, why we weigh delivery alongside dating, and what to know when the supply you write is longer than the date.
What a beyond use date is
A beyond use date, or BUD, is the date after which a compounded preparation should not be used. It is set by the pharmacy from stability and microbial considerations, and it is not the same thing as a manufacturer's expiration date.
Expiration dates belong to manufactured products that have been tested under FDA review. A BUD belongs to a compounded preparation and is counted in hours, days or months from the date and time the preparation is compounded, not from the day the patient receives it.
That last point matters in practice and we return to it below. The clock starts at compounding, so time spent in transit counts against it.
A beyond use date is a property of a formula in its container, not a feature of the pharmacy that prepared it. The same active in a different base, a different container or a different strength can carry a different date, and each date can be correct for the formula it belongs to.
How USP 795 sets the default dates
When no USP monograph or preparation specific stability data exists, USP 795 assigns default beyond use dates by water activity: 14 days for non preserved aqueous preparations, 35 days for preserved aqueous, 90 days for nonaqueous oral liquids, and 180 days for other nonaqueous forms.
| Preparation type | Water activity | Default BUD |
|---|---|---|
| Non preserved aqueous | 0.6 or above | 14 days, refrigerated |
| Preserved aqueous | 0.6 or above | 35 days |
| Nonaqueous oral liquid | Below 0.6 | 90 days |
| Other nonaqueous forms, including topicals, suppositories, troches and capsules | Below 0.6 | 180 days |
Defaults assume tight, light resistant containers. A BUD cannot exceed the shortest remaining expiration date of any component, and the pharmacist may assign a shorter date than the default.
These are ceilings, not targets. A date of 30 days sits comfortably inside the 35 day default for a preserved water containing preparation, and it is a common and appropriate choice for many of them.
Water activity is the reason the base matters so much. Free water supports microbial growth and drives chemical breakdown of many actives, so a preparation with very little free water can carry a longer default. Our guide to anhydrous compounding bases covers that science in detail.
How a longer date is earned
A date longer than the default requires a stability study using a stability indicating method on the same formulation in the same type of container, and without a USP monograph the date cannot exceed 180 days. A professional judgment alone is not enough.
USP 795 sets out what a supporting study has to show. These are the main requirements.
- A stability indicating analytical method for the active ingredient, one that can tell the intact drug from its breakdown products.
- The same formulation, meaning the same active, base and strength or a bracketed range that includes it.
- The same container closure material that will be used to dispense.
- For a water containing preparation, antimicrobial effectiveness testing under USP chapter 51 at the end of the date.
- A date no later than the shortest expiration of any component.
USP has confirmed that a study meeting these requirements can support an extended date whether it is published or unpublished.
What bracketing means
A bracketed study tests a low and a high strength of the active. Both are tested in the same base and container, and the result supports any strength between them. That is how one study can cover a range of prescriptions written at different strengths.
Which bases allow longer dates
Water status sets the starting point and a stability study decides whether a preparation can go beyond it: anhydrous bases begin at 180 days for most forms, while water containing bases begin at 14 or 35 days and can be extended by a formula specific study up to 180.
| Base type | Water status | Default date | What can change it |
|---|---|---|---|
| Anhydrous topical and transdermal bases, such as PermE8 and WO6 | Below 0.6 | 180 days | Already at the ceiling. A shorter date applies if an active or component requires it. |
| Anhydrous vaginal base, Ellage | Below 0.6 | 180 days | Same as above |
| Anhydrous hormone base, Anhydrous VersaBase HRT | Below 0.6 | 180 days | Same as above |
| Anhydrous oral suspension, Anhydrous SuspendIt | Below 0.6 | 90 days | A formula specific study can support up to 180 days |
| Water containing oral suspension, SuspendIt | Aqueous | 14 or 35 days | Published studies of specific actives report dates near 180 days |
| Water containing creams, gels and hydrogels | Aqueous | 14 or 35 days | A formula specific study with antimicrobial effectiveness testing, up to 180 days |
The anhydrous classification belongs to the finished preparation. Adding an aqueous ingredient can raise water activity above 0.6 and change the category.
What published stability studies report
PCCA publishes stability studies for specific formulas, and several report dates close to 180 days in a water containing suspension base, which shows how a formula specific study can carry a preparation well past the default.
Studies of compounded suspensions in the PCCA base SuspendIt reported physical and chemical stability for 181 days for ursodiol, 185 days for amitriptyline hydrochloride and 180 days for allopurinol, with microbial testing under USP chapter 51 in the studies that included it. Each used a stability indicating method and a bracketed concentration range.
PCCA describes its FormulaPlus program as studying the beyond use date of compounded formulas using stability indicating assays, with USP 51 antimicrobial effectiveness testing where applicable. According to PCCA, the program includes more than 225 extended date formulas, adds about 20 new studies each year, and includes about 75 bracketed studies.
The same approach underlies published work on topical bases. A study in Pharmaceutics validated a stability indicating assay supporting beyond use dating for compounded testosterone topical gels, and our article on why the base changes the prescription describes it.
A date from a study applies to the active, base, container and strength range that were tested. It does not transfer to a different active, a different base or a strength outside the bracket. That is why we confirm which formula and which date apply before a prescription is filled.
Why 180 days is not the only factor
A longer date and better delivery are separate properties of a base, so we weigh dating alongside permeation, the active ingredient, the route and what the patient will actually use. Choosing a base on the date alone would leave out half the picture.
PCCA's laboratory testing illustrates why. In its in vitro testing, PermE8 delivered ketoprofen comparably to Lipoderm and at roughly four times the level of Anhydrous Lipoderm. Those are two bases from one family, and they differed in how much active crossed the test membrane. An anhydrous version of a base is not automatically the equivalent carrier of the original.
That testing is laboratory permeation data. It compares how much drug crosses a membrane under controlled conditions and does not establish how a patient will respond. It is still the best available guide to how bases differ, and it is a reason to treat a change of base as a formulation decision.
| Factor | Why it enters the choice |
|---|---|
| Beyond use date | Sets how much can be dispensed at once and how often a patient refills |
| Delivery | Bases differ in how much active crosses skin or mucosa in laboratory testing |
| Active ingredient | Some actives degrade in water or need a particular base to stay stable |
| Route | Topical, vaginal and oral preparations call for different bases |
| Feel and acceptability | A preparation the patient dislikes is not used as directed |
| Storage | Refrigeration and container type affect what is practical at home |
How we use bases that allow 180 days
Where a prescription can be made in more than one base, we tell the prescriber which options exist, the date each supports and what is known about delivery for each, then prepare the one the prescriber chooses. The date is one input, not the deciding one.
As a PCCA member pharmacy, Mixwell has access to PCCA's published base technology and its stability studies. That widens the options available for a given prescription, and we think prescribers are better served by seeing the options than by receiving a single default.
- We start from the prescription: the active, the strength, the route and the patient.
- We identify the bases that suit the active and route, and note the date each supports, whether from the USP default or a formula specific study.
- We share what laboratory data exist on delivery for those bases, and say plainly where none exist.
- The prescriber chooses. If you write pharmacist's choice, we tell you which base we used and the date it carries.
- We assign the date from the formula, container and storage conditions, and print it on the label.
Our article on why Mixwell compounds with PCCA formulas describes the wider quality process, and our omeprazole oral suspension guide shows how a bracketed study works for one real formula.
Want to see the date each base option would carry for a prescription you are writing?
Call (909) 378-7301When the supply is longer than the date
A days supply and a beyond use date are two separate numbers, and a 90 day supply cannot be dispensed in a single fill of a preparation dated for 30 days. Knowing this before you write saves a call and a delay for the patient.
A 30 day date is not a defect. It is the right answer for many water containing preparations, for actives that break down in water, and wherever no study supports a longer date for that exact formula. The question for the prescriber is how to match the supply to the date.
- The date runs from compounding, so shipping time counts against it.
- The patient discards the preparation on the date shown, even if some remains.
- Quantity per fill should match the date, not the full course you intend.
- Controlled substances carry their own limits on refills and supply.
- Changing base to reach a longer date is a formulation change, because delivery can differ between bases.
| Option | What it means | What to weigh |
|---|---|---|
| Smaller fills with refills | Each fill is compounded separately and carries its own date. Write the quantity per fill and the number of refills. | More fills and shipments, with the same formula throughout |
| A formula with a longer validated date | If a suitable base or formula supports a longer date for that active, a larger supply becomes possible. | Delivery can differ between bases, so treat it as a formulation decision |
| A different dosage form | A different form can carry different default dating. | It changes the route and absorption, so it is the prescriber's call |
When a patient's prescription arrives with a supply longer than the date, we call the office to confirm which option you want rather than guessing. A short call up front is faster than a correction afterward.
Writing the prescription with the date in mind
State the quantity per fill and the number of refills, name the base or write pharmacist's choice, and call us if you want a longer supply than a single fill can carry. Those details settle most dating questions in advance.
- Write each active with its strength and the dosage form.
- Name the base, or write pharmacist's choice and we will tell you which we used and its date.
- State the quantity per fill and the number of refills, so the total supply matches your intent.
- Note the patient's storage constraints, such as limited refrigerator space.
- Call (909) 378-7301 to confirm the date the formula carries before you write a long supply.
For the broader picture, see our prescriber's guide to writing compounded prescriptions in California.
Serving prescribers in California
Mixwell Compounding Pharmacy is a PCCA member pharmacy in Chino, CA, performing non sterile compounding only. We work with prescribers across the Inland Empire, Los Angeles County and Orange County, and deliver across California.
- Chino
- Chino Hills
- Ontario
- Rancho Cucamonga
- Upland
- Pomona
- Diamond Bar
- Corona
- Riverside
- Eastvale
- Brea
- Fullerton
Common questions
What is a beyond use date in compounding?
A beyond use date is the date after which a compounded preparation should not be used. It is assigned by the pharmacy from stability and microbial considerations and is counted from the date and time of compounding.
How is a beyond use date different from an expiration date?
An expiration date applies to a manufactured product tested under FDA review. A beyond use date applies to a compounded preparation and is set by the pharmacy, either from the USP default for its category or from a stability study of that formula.
How long can a compounded preparation last?
Without a monograph or formula specific study, USP 795 defaults are 14 days for non preserved aqueous, 35 days for preserved aqueous, 90 days for nonaqueous oral liquids and 180 days for other nonaqueous forms. A stability study can support a longer date, up to a maximum of 180 days unless a USP monograph allows more.
Why do some preparations have a 30 day date and others 180 days?
The date follows the formula. A water containing preparation starts from a shorter default, while a preparation with very little free water starts from a longer one. Some actives also degrade in water, and some formulas have a stability study that supports a longer date. A shorter date is not a lower standard.
Is a longer beyond use date always better?
No. A longer date reduces how often a patient refills, but it is only one property of a base. Delivery, the stability of the active, the route and what the patient will use also matter, and bases can differ in how much active crosses skin in laboratory testing.
What if my prescription is for 90 days but the beyond use date is 30?
The supply cannot be dispensed in one fill. Options include smaller fills with refills, a formula that supports a longer validated date where one is suitable, or a different dosage form. Call us before writing so we can confirm which fits.
Can a pharmacy simply extend a beyond use date?
Only with a stability study that meets USP 795 requirements: a stability indicating method, the same formulation and container, and antimicrobial effectiveness testing for water containing preparations. The date cannot exceed the shortest component expiration or 180 days without a monograph.
What is a bracketed stability study?
A bracketed study tests a low and a high strength of the active in the same base and container. The result supports any strength between them, so one study can cover a range of prescriptions.
Does Mixwell accept insurance, and can I use an HSA or FSA?
Mixwell does not accept insurance. Compounded medications for people can generally be charged to an HSA or FSA account. Call (909) 378-7301 for pricing.
Key Takeaways
- A beyond use date belongs to a formula in its container, so different dates for different preparations can each be correct.
- USP 795 defaults run from 14 days for aqueous to 180 days for most nonaqueous forms, and a stability study can extend a date up to a maximum of 180 days.
- Anhydrous bases begin at the 180 day ceiling for most forms, while water containing bases begin shorter and need a formula specific study to go further.
- Longer dating and better delivery are separate properties, so we weigh permeation, the active and the route alongside the date.
- The date runs from compounding, so match the quantity per fill to it and call us before writing a supply longer than the date.
Sources
- United States Pharmacopeia. General Chapter 795, Pharmaceutical Compounding, Nonsterile Preparations, Section 10 Establishing Beyond Use Dates and Table 4. Official November 1, 2023.
- United States Pharmacopeia. General Chapter 795 frequently asked questions, including extending beyond use dates with a stability indicating study, published or unpublished.
- PCCA. FormulaPlus stability studies, including stability indicating assays, USP 51 antimicrobial effectiveness testing and bracketed studies. pccarx.com
- PCCA. What goes into a PCCA formula. PCCA Blog, 2025. pccarx.com
- PCCA. Publications index by product, including SuspendIt and Atrevis journal articles. pccarx.com
- Stability of compounded ursodiol suspensions in PCCA base, SuspendIt, with companion studies of amitriptyline hydrochloride and allopurinol in SuspendIt. PCCA publications index.
- Testosterone therapy for late onset hypogonadism: a clinical, biological, and analytical approach using compounded testosterone topical gels. Pharmaceutics. 2024;16(5):621. mdpi.com
- PCCA. PermE8 Anhydrous Gel and Anhydrous Family product information. pccarx.com
- U.S. Food and Drug Administration. Compounding and the FD&C Act, Section 503A.