Could someone please explain to me how to calculate the dose for sulfamehoxazole and trimethoprim (Bactrim)? I looked it up in the unit's pediatric dosage handbook, but i'm confused because it says to calculate it as TMP/mg/day. I know TMP stands for trimethoprim but i'm unsure how to obtain the TMP value.. I only ask because I was calculating a dose for my patient and I questioned the physician on the dose because it seemed too high. In turn, the physician stated that it was the correct dose and it was too complicated to explain.