Reconstitution of vancomycin powder?

Question

How would 500mg of vancomycin powder be reconstituted to form 10mg vancomycin in 4ml water for an intrathecal injection?

Answer 1

More than likely the 500mg is your stock, and if it is your whole stock of vancomycin you probably do not want to use it all for one injection.

This reconstitution is as easy as it sounds - weigh out 10 mg of the vancomycin powder. You should have about 2ml of distilled (possibly double distilled or milli q) water in a beaker or flask on a stir plate. Make sure that the beaker or flask or whatever has been autoclaved. Drop a stir bar in the beaker or flask, add the 10 mg of vancomycin powder, and then add another 2 ml of your purified (distilled, double distilled or milli q) water.

Once the vancomycin dissolves (you may need to check its limits of solubility), you will have your 10mg vancomycin in 4ml water. Remove stir bar, and fill syringe. More than likely you will need much less than 4ml, as most intrathecal injections (at least in mice and rats) are in the 5 -300 microliter range. If this is the case, and you need much less volume,  you can tweak the amount of vancomycin to adjust for using less water.

As a side note - the reason why purified water may be more desirable than an isotonic solution (saline) may be for the potential solubility limitations of the powder.

Answer 2

Dissolve the 500 mg into 200 cc of water.

Each cc will contain 2.5 mg of vancomycin.

Thus 4 cc will contain 10 mg.

Not sure I'd inject that into anything. Surely you would use an isotonic solution? But hey, I'm a scientist, not a pharmacist.