Our office manager has instructed us to physically draw up injectable controlled drugs during weekly cycle counts, in order to better measure them. Is this a good idea?

I can’t point to any specific DEA rule or regulation that prohibits such a procedure. It’s possible that the procedure is prohibited in your state’s Pharmacy Act, but from a practical standpoint, withdrawing sterile medication from a multi-dose vial to accurately measure the contents is not a good idea for at least 3 reasons:

First, there is always the possibility of introducing contamination into the substance every time one probes the stopper, withdraws medicine or reinjects it back into the vial. Sure, sterile technique is possible, but there’s always the chance of human error in that technique.  Reintroducing sterile materials back into a vial once withdrawn is considered poor pharmacological technique.

Second, there’s the possibility of an accidental spill.  The chances are low but they are not zero.  Even with locking hub syringes and needles, there’s always a chance the needle will “blow off” the syringe when pressure is applied to reinject the drug back into the vial. There’s a possibility of human error when the staff member loses control of the syringe and it  falls out of the vial and becomes contaminated.  There’s always the possibility that something will happen and the drug accidentally gets expelled from the syringe.

Third, there is the issue of unnecessary waste.  Every time a drug is withdrawn from a vial into a syringe, a certain amount of the drug is forever trapped in the syringe.  We often call this hub waste, but it’s really an amount that sticks to the entire interior of the syringe and is never expelled.  Although that amount is relatively insignificant, the loss could add up in smaller vials that are not used very frequently but are “inventoried” on a regular basis with a syringe withdrawal method.

All things considered, the “withdrawal and reinjection” method of measuring sterile liquid medications is not recommended.  The weight loss method or the marking gauge method are more appropriate ways to measure sterile liquid medications.

Excerpted from The Complete Veterinary Practice Controlling Controlled Drugs Manual:

To make a measuring gauge specifically for a bottle of a given drug, start by gathering materials: an EMPTY bottle of the size and shape currently used for the drug, a syringe with attached needle and a piece of stiff cardstock similar to the backing from a writing tablet.

1. Using the syringe/needle, inject 1 milliliter of tap water into the bottle.  Stand the card upright next to the bottle and make a mark on the card corresponding to the level of the fluid in the bottle.  Add another milliliter of water and make another mark at the correct level.  If the bottle is small or the drug is used in very small increments, it may be useful to make graduation marks in ½ milliliter increments.  Continue this process until the bottle is full.  If the liquid level continues up the neck of the bottle, contour the cardboard to the bottle.
   

2. Mark the cardboard template with the bottle type or drug name and keep it with the log.  It'll probably be necessary to make a template for each drug since manufacturers and bottles will differ.  Then when it's time to inventory opened bottles of controlled substances, just place the bottle on a flat surface, put the gauge next to the bottle and read the level.  No guessing and no chance of contaminating the bottle.
   

3. Be sure to withdraw and discard the tap water from the bottle and dispose of the empty bottle.

The weight loss method is useful in counting tablets or liquids but is dependent on a scale that is calibrated in tenths of grams for required accuracy.