The maximum effective BUD allowed after the required standard sterility quarantine period is 28 days.
BUDs based on well-designed c GMP stability studies and sterility testing per (USP ) are sufficient to support extended BUDs up to at least 90 days.
The 42 day maximum proposed by USP is arbitrary and inconsistent with the preponderance of experience related to compounding with manufacturer-prepared sterile ingredients and especially automated robotic IV compounding which insures a repeatable and monitored process to produce specific CSP formulations.
One of the first issues dealt with was the terminology.
The familiar "Expiration Date" terminology was replaced with "Beyond-use Date" (BUD).
These are often due to inadvertent mislabeling of containers and medication vials, incomplete blending or trituration, breakdown of the actives, unknown impurities in the actives, accidental double weighing of the active, failure to include the active, misreading of labels and adding the wrong form of the active, failure to account for % water in the active, and more. (See below for other quotations from the USP)We have had extensive experience in performing potency assays on all kinds of formulations and dosage forms, from capsules to creams and gels, injectables to IV solutions,to troches, lozenges, suppositories, pellets, and more.
The only way to know if such problems exist is through testing, especially through the use of an independent outside laboratory. Each sample you submit is individually evaluated for the best means of analysis.