In the compounding room, controlled substance waste is a routine byproduct of preparing patient-specific doses: the unused remainder of a vial, overfill drawn back from a syringe, or a preparation that fails final inspection. Each of those events removes drug from inventory without it reaching a patient. When one person withdraws the drug, prepares the dose, and records how much was discarded, the waste log shows only what that person chose to write. That makes single-signature logs the easiest control in the pharmacy to falsify. Requiring a second qualified staff member to watch and co-sign every waste event turns the record from a self-report into an independently verified transaction.
How to Implement Two-Person Witnessing
Start with a written policy that defines a waste event broadly: any quantity of controlled substance removed from inventory for compounding that is not incorporated into the final preparation. The policy should name who may serve as a witness, such as a pharmacist or a technician authorized for controlled substance handling, and it should bar the preparer from witnessing their own waste. The witness must see the waste itself, including the drug, concentration, measured volume, and disposal into an approved non-retrievable container. Signing afterward on the preparer's word does not count. Prohibit pre-signed logs and retrospective witnessing outright.
Plan for how the compounding room actually operates. Garbing and access requirements under USP <797> may limit who can enter the buffer area, so decide in advance whether witnesses will garb in or observe through a viewing panel that gives a clear line of sight. Staff so that a witness is available during all compounding hours. A typical workflow looks like this:
- The preparer records the drug, strength, lot, and quantity removed from inventory.
- Before discarding anything, the preparer calls the witness. Together they confirm the product and calculate the expected waste (quantity removed minus quantity in the final preparation).
- The witness watches the waste volume being measured and discarded into the approved waste container.
- Both staff members sign or authenticate at the time of the event, recording the date, time, volume, reason, and preparation identifier.
- A pharmacist reviews the daily reconciliation of quantities removed, compounded, and wasted.
Warning Signs to Watch For
Two signatures only protect the process if the second signature is real. During waste audits, look for these patterns:
- The same pair of staff members witnessing each other's waste far more often than scheduling would explain.
- Witness entries made in batches, such as several signatures timestamped together at the end of a shift.
- Waste recorded while the witness was not present, according to badge access, shift schedules, or login records.
- Waste volumes that regularly exceed the calculated expected waste, or that run higher for one preparer than for peers compounding similar doses.
- Frequent "witness unavailable" exceptions tied to one person or one shift.
Documentation Tips
Record waste at the time it happens, and link each entry to a specific preparation record so auditors can match it against the compounding log. Include an expected-waste field so any difference between calculated and actual waste is visible on the record itself. In electronic systems, each person must authenticate with their own credentials. A preparer who enters a coworker's password has defeated the control completely, so treat credential sharing as a policy violation. Keep waste records with your other controlled substance records for at least two years, as 21 CFR 1304.04 requires, or longer if your state requires it. Some organizations also send a sample of waste for testing now and then to confirm it is the labeled drug and has not been diluted or substituted. Build these requirements into your policy templates and score them with the DivertGuard diversion prevention checklist.
Regulatory Grounding
21 CFR 1301.71(a) requires every DEA registrant to provide effective controls and procedures to guard against theft and diversion of controlled substances. 21 CFR 1304.21(a) requires complete and accurate records of controlled substances received, dispensed, or otherwise disposed of. For destruction of controlled substance inventory, 21 CFR 1304.21(e) requires a DEA Form 41 record signed by the two employees who witnessed the destruction. DEA generally treats wastage of a partially used dose differently from inventory destruction, so federal rules may not directly require a second witness for every compounding waste event. Two-person witnessing still applies the same standard DEA sets for destruction, and some state boards of pharmacy require witnessed waste explicitly, so check your state's rules. If an audit finds waste discrepancies that point to theft or significant loss, 21 CFR 1301.76(b) requires notifying DEA within one business day; see the DEA Form 106 guide.
Frequently Asked Questions
Q: Can a witness sign after the fact if they trust the preparer?
A: No. A witness signature certifies that the witness saw the waste. Signing on trust puts a false statement in a controlled substance record, and it removes the independent check the control is meant to provide.
Q: What should happen if no witness is available?
A: Seal the waste in a labeled, tamper-evident container, store it securely, and complete witnessed disposal as soon as a witness is available. Document the reason for the delay. If this happens often, treat it as a staffing problem to fix, not as a routine exception.
Q: Does electronic witness authentication satisfy the control?
A: It can, if each person authenticates with unique credentials at the time of the event and the system records a timestamp. Electronic signatures are only as reliable as the credential practices behind them, so audit them just as you would paper logs.