1.4 Immediate-Use CSPs: The 4-Hour Rule and Its Conditions
Key Takeaways
USP <797> (official November 1, 2023) calls this provision immediate-use CSPs; there is no 'urgent-use' category in the chapter.
An immediate-use CSP may involve no more than 3 different sterile products, and administration must begin within 4 hours after preparation starts.
Unless the preparer administers the dose or witnesses its administration, the label must show every active ingredient and amount, the preparer's name or initials, and the 4-hour window.
Unused starting components from a single-dose container must be discarded after the preparation is complete; a single-dose container is never used for more than one patient under this provision.
The 2008 limits of 1 hour, 2 entries per container and 'emergency only' use are gone. Immediate-use CSPs may even be batched, if every condition is met.
1.4 Immediate-Use CSPs: The 4-Hour Rule and Its Conditions
Important
The chapter term is immediate-use CSP. Exam items may test whether you know the current conditions or the retired 2008 ones, such as the 1-hour limit and the 2-entry limit. Learn the current list exactly.
Why the provision exists
Some sterile doses must be mixed where and when the patient needs them, for example in a code, in the operating room, or in the emergency department. Taking every such dose to a cleanroom would delay care. USP <797> Section 1.3 therefore says that compounding for direct and immediate administration is not subject to the Category 1, 2 or 3 requirements, provided that all of the conditions below are met. If any condition is missed, the preparation is an ordinary CSP and must meet the category rules, including an ISO Class 5 PEC.
The seven conditions (USP <797> Section 1.3)
| # | Condition | What it means in practice |
|---|---|---|
| 1 | Aseptic techniques, processes and procedures are followed, and written SOPs are in place | SOPs must minimize contact with nonsterile surfaces, particulate or biological-fluid contamination, and mix-ups |
| 2 | Personnel are trained and have shown competency in aseptic processes for their tasks | The facility's SOPs set how competency is assessed; USP sets no frequency and does not require media fills |
| 3 | The preparation follows evidence-based compatibility information | Approved labeling, stability and compatibility studies |
| 4 | Not more than 3 different sterile products | Several containers of the same product count as one product |
| 5 | Unused starting components from a single-dose container are discarded when the preparation is complete | A single-dose container must not be used for more than one patient |
| 6 | Administration begins within 4 hours after preparation starts | If it has not begun by then, the CSP is promptly and safely discarded |
| 7 | Labeling, unless the preparer administers the dose or witnesses its administration | Names and amounts of all active ingredients, the preparer's name or initials, and the 4-hour period |
Counting "3 different sterile products"
USP's FAQ gives worked examples. Two vials of the same drug reconstituted with two vials of Sterile Water for Injection and added to one bag of 0.9% sodium chloride uses three different products (the drug, the water and the saline). Four vials of one drug added to one bag uses only two different products. Count product identities, not containers.
- Compliant: norepinephrine vials + one 250 mL bag of dextrose 5% (2 different products).
- Not compliant: a bag of sterile water + sodium chloride concentrate + potassium chloride + calcium gluconate (4 different products). This must be prepared as a Category 1 or higher CSP in an ISO Class 5 PEC.
The 4-hour clock
- The clock starts at the start of preparation, not when mixing ends or when the dose reaches the bedside.
- Only the start of administration must fall inside the 4 hours. An infusion that begins at hour 3 may run for its ordered duration.
- The 4-hour window is USP's microbiological limit. It rests on the roughly 4-to-6-hour lag phase before introduced bacteria start to multiply. It does not override a shorter chemical stability limit in the product labeling.
- A facility may keep a stricter 1-hour policy. USP's FAQ says that choice is acceptable.
Labeling
A label is required unless the person who prepared the CSP directly administers it, or witnesses its administration. When required, the label shows:
- The names and amounts of all active ingredients
- The name or initials of the person who prepared it
- The 4-hour time period within which administration must begin (for example, "Prepared 14:15 - begin by 18:15")
Patient identifiers are normally added under institutional policy, but they are not one of the three USP <797> immediate-use label elements.
What changed from the 2008 chapter
| Feature | 2008 immediate-use | Current immediate-use (2022 revision, official 2023) |
|---|---|---|
| Administration deadline | Begin within 1 hour of preparation start | Begin within 4 hours of preparation start |
| Product limit | Not more than 3 commercially manufactured sterile, nonhazardous products | Not more than 3 different sterile products |
| Container entries | Not more than 2 entries into any one container | No entry limit in the chapter |
| Scope | Emergencies or immediate administration where cleanroom preparation would harm the patient | Any CSP for direct and immediate administration that meets all conditions |
| Batching | Not contemplated | Allowed for one or more patients if every condition is met; a compounding record is then required |
Because the chapter now allows immediate-use doses to be batched, a CSP made for more than one patient needs a compounding record (USP <797> Section 11.2).
Hazardous drugs
Section 1.3 of USP <797> does not itself mention hazardous drugs. USP <800> still applies, though. It requires sterile hazardous drugs that need manipulation, including every NIOSH Table 1 antineoplastic and any hazardous drug active pharmaceutical ingredient (API), to be compounded in an externally vented C-PEC inside a C-SEC. Only a documented assessment of risk can allow alternative containment for eligible dosage forms. So reconstituting methotrexate or cyclophosphamide at a nursing station as an "immediate-use" dose violates USP <800>, even though the USP <797> exemption is silent on hazardous drugs.
Common traps
- Using the old term or old limits. There is no 2-entry rule and no 1-hour rule in the current chapter.
- Timing the clock from arrival on the unit. The clock runs from the start of preparation.
- Reusing a single-dose vial for the next patient. Leftover single-dose components are discarded when the preparation is complete.
- Assuming media-fill tests are required. For staff who make only immediate-use CSPs, the facility's SOPs define how competency is evaluated.
- Treating the exemption as permission for poor technique. Aseptic technique, SOPs and evidence-based compatibility are all still required.
At 10:15, an ICU nurse begins preparing a norepinephrine infusion from vials and a bag of dextrose 5% as an immediate-use CSP. Under USP <797>, by what time must administration begin?
11:15, because immediate-use CSPs must be given within 1 hour
12:15, because the clock starts when mixing is finished
14:15, 4 hours after preparation started
22:15, the 12-hour Category 1 limit
Which proposed immediate-use preparation fails a USP <797> Section 1.3 condition?
Four vials of the same antibiotic added to one bag of 0.9% sodium chloride
A vial punctured three times while drawing up one patient's dose
Leftover drug in a single-dose vial saved for the next patient's dose later in the shift
A dose batched for two patients in the same unit, with a compounding record
An emergency department pharmacist prepares a sedation infusion as an immediate-use CSP, and a different nurse will hang it in the trauma bay. Which set of label elements does USP <797> Section 1.3 require?
Patient name, medical record number and a 24-hour refrigerated BUD
Active ingredients and amounts, the preparer's name or initials, and the 4-hour period for starting administration
Lot number of every component and the Designated Person's signature
A sterility test reference number and the date of the last media fill
Sections you finish are checked off in the contents.