The following USP 797 Q&A helps answer your questions.
USP 797 refers to chapter 797 "Pharmaceutical Compounding – Sterile Preparations," in the USP National Formulary.
There is never a shortage of questions about Immediate-Use CSP’s, so today I’ll post a thorough review of the provision, including the six specific criteria that must be met to qualify as immediate use from USP Chapter 797 itself (and this usually answers most of the questions), distilling it down to a few bullet points, and adding several FAQ’s from USP’s website.
First the criteria: The immediate-use provision is intended only for those situations where there is a need for emergency or immediate patient administration of a CSP.
Compounding in worse than ISO Class 5 (see Table 1) conditions increases the likelihood of microbial contamination, and administration durations of microbially contaminated CSPs exceeding a few hours increase the potential for clinically significant microbial colonization and thus for patient harm, especially in critically ill or immunocompromised patients.
Finally, some questions from the FAQ page on USP 797’s website: 2.
While the safety of compounded sterile preparations (CSPs) has been an important topic in the practice of pharmacy for decades, the recent tragic deaths related to fungal contamination of preservative-free methylprednisolone injection have once again put the topic on the national stage.
USP Chapter 797 describes the procedures and requirements for compounding sterile preparations and sets the standards that apply to all settings in which sterile preparations are compounded.
Opened or needle-punctured single-dose containers, such as bags, bottles, syringes, and vials of sterile products and CSPs shall be used within 1 hour if opened in worse than ISO Class 5 air quality, and any remaining contents must be discarded.
Single-dose vials exposed to ISO Class 5 or cleaner air may be used up to 6 hours after initial needle puncture.
Preparations that are medium-risk level and high-risk level CSPs shall not be prepared as immediate-use CSPs.
Immediate-use CSPs are exempt from the requirements described for Low-Risk Level CSPs only when all of the following criteria are met: 1.