I've tried to find the answer to this online without success. I know that when reconstituting powdered drugs like cefazolin you need to account for the powder volume but I don't know if you have to do the same for liquid preparations when you've diluted them into iv solutions. i.e. If you have 20mL of a drug diluted in 1000mL of glucose 5% to run over 6 hours through a macro drip set, do you calculate the drop factor by using 1000mL or 1020mL as the volume? I realise the difference is minimal (56 vs 57 dpm) but for exam purposes does anyone know the definitive answer?