You do not need to memorize a formula to know this, as long as you know the units (which are SO much easier to remember as they are intuitive). The answers are mostly clearance and steady state, which means you can cancel units to see if the answer choice makes sense.
For example, since CL has units of L/min and Css has units of mg/L, then (A) works out because L/min x mg/L = mg/min which is the correct units for infusion rate.
Whereas (B) CL/Css would not work because those units would be L/min / mg/L = L^2/min*mg, which does not make sense.
So if you just cancel some units, you can answer many of the questions.
Huge disclaimer: this won't work with things like half-life, because there is a factor of Ln(2) that has no units, so you have to memorize formulas that have factors before them.
FWIW, I committed this shortcut equation to memory: Steady State (Css) = Infusion Rate / Clearance (CL)
To me, this makes sense. Steady State equals the volume in divided by the volume out. Flip this bad boy around and it leaves you with Infusion Rate = CL * Css
submitted by โjoha961(45)
Maintenance dose = (Css * CL * t) / F... where
tis elapsed time between doses (not relevant here since itโs continuous infusion) andFis bioavailability (which is 100% or 1.0 here because itโs given IV).โContrast with loading dose:
... where
Vdis volume of distribution.