Basic Drug Calculations: How to Survive Clinical Rotations #4
When I matriculated into clinical rotations, the thing that I probably was most terrified of was messing up a drug dosage or calculation. So much math, and when you are stressed? It can be easy to mess up! So let’s go through a basic drug calculation together!
-First things first: Unless it’s a very specific drug that states otherwise, in general, ALL OF YOUR WEIGHTS WILL NEED TO BE IN KGS (kilograms), NOT POUNDS!!!!! How do you do this? Take your weight in pounds and divide by 2.2!! So a 14 pound dog is 6.36kgs!!!!
Okay, so you have a 14 pound dog (6.36 kg) named PooPoo that you want to give Miraclemycin to that is in a bottle. It states in your pharmacy book (Drugs R Us) that you should give 3.0 mg/kg of MIraclemycin. That means you need 3.0 mg (MILLIGRAMS) PER KILOGRAM of body weight. We just that PooPoo is 6.36 kgs, so simply multiply THE WEIGHT (IN KGS) BY THE MGS PER KILOGRAM. That is 3.0 mg/kg X 6.36 kg to get 19.08 mgs! Whoohoo, we know how much to give!!!
…But it’s in a bottle that is liquid and it says that the bottle has 15 mg/ml… Never fear! This means there is 15 MG (milligrams) of medication per 1 ML (Milliliter) of liquid. So if we want 19.08 milligrams, we take the amount of milligrams we want divided by how many MG/ML. So 19.08 mg divided 15 mg/ml= 1.2 mls! That means we would draw up 1.2 mls in our syringe!
(Below is the calculation again in a little more streamlined fashion):
14 pounds / 2.2 = 6.36 kgs
6.36 kgs X 3.0 mg/kg = 19.08 mgs
19.08 mgs/ 15 mg/ml = 1.2 mls of Miraclemycin!