Controlled-drug waste from a partially used MLK bag
You built the MLK bag from problem 4 (50 mg morphine, 400 mg lidocaine, 100 mg ketamine in 250 mL). The patient was extubated and recovered well after ~15 hours and the CRI was discontinued with 100 mL remaining in the bag. How much of each controlled drug needs to be logged as waste?
Hint
The bag is a uniform mixture. If you know the fraction of the bag that wasn't given, that same fraction of every drug in the bag was wasted.
Another hint
Wasted fraction = volume remaining ÷ bag volume. Then for each drug: mg wasted = total mg in bag × wasted fraction. Lidocaine isn't federally controlled, but the math is the same.
Show worked answer
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First, identify the wasted-volume fraction. 100 mL of a 250 mL bag = 100 / 250 = 0.4, or 40 % of the bag was wasted.
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Each drug in the bag is wasted proportionally. Morphine wasted = total mg × wasted fraction. mg stays, the dimensionless fraction multiplies through.
$$50 \,mg \times 0.4 = 20 \,mg \text{ morphine (C-II)}$$ -
Same approach for ketamine.
$$100 \,mg \times 0.4 = 40 \,mg \text{ ketamine (C-III)}$$ -
Lidocaine is not federally controlled, but you can compute it the same way for completeness.
$$400 \,mg \times 0.4 = 160 \,mg \text{ lidocaine}$$ -
Optional: stock-equivalent volumes for logs that record mL. Divide each wasted mg by its stock concentration.
$$\tfrac{20\,\cancel{mg}}{5\,\cancel{mg}/mL} = 4\,mL \text{ morphine stock-equivalent}$$ -
The physical waste is 100 mL of diluted bag mixture, not undiluted stock. Most controlled-drug logs want the mg figure since that's what reconciles against your inventory.
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On the schedules: morphine is DEA Schedule II (C-II), a full µ-agonist opioid with high abuse potential and accepted medical use. Ketamine is Schedule III (C-III). Both require controlled-drug logging; lidocaine is not federally scheduled. State scheduling can differ, and individual practices may have stricter internal policies.
Log 20 mg morphine (C-II) and 40 mg ketamine (C-III) as waste. Lidocaine is not federally controlled but 160 mg was discarded with the bag.