Looking for some advice from nurse math lovers! Thanks in advance :)
When reconstituting a drug, I generally use the information supplied on the monograph or drug insert. (i.e. Add 2.5 mL to a 1 gram vial to achieve a concentration of 330 mg/mL... or whatever). After I reconstitute, then I take the dose I need and dilute it further....
However, the nursing department is coming up with a new way of reconstituting... simply by adding 9 mL to a 1 g vial..... i.e. In order to dilute cefazolin to 1 g/10 mL: the answer key states -- add 9 mL to a 1 g vial to achieve a concentration of 1 g/10 mL.
My interpretation: This might work if the required dose = the entire 1 gram. However, for smaller doses, it would be inaccurate to assume that the final concentration is 1 g/10 mL (because this would mean that the drug would have to have a density of 1g/mL.... but usually the drug's density is > 1 g/mL, which can be inferred from the reconstitution information on the monograph!!) i.e. If we add 2.5 mL to a 1 gram vial, if the density of the drug is 1 gram/mL, we should have a final concentration of: 1000 mg/(2.5 mL + 1 mL)... but this is LESS than the ACTUAL concentration on the monograph. Likewise, 1 g/10 mL is LESS than the ACTUAL concentration..... This wouldn't matter if we need the entire 1 gram, but it WILL MATTER if we need a SMALLER dose!
Does anyone understand what I am talking about? If you do, please help me understand further! Personally, I think it is MORE ACCURATE to reconstitute ACCORDING to the MONOGRAPH rather than simply adding 9 mL, especially when smaller doses are required and we do not know for sure that the drug's density is 1 gram/mL!
