Extremistan
Weight-based drug dosing for hydrophilic medications may produce excessive serum concentrations in obese patients so alternatives to total or actual body weight are sometimes recommended. Please cite the equation for ideal body weight (for a man or a woman)
45.5 + 2.3(every inch over 60 inches) (women) or
50 + 2.3 (every inch over 60) (men)
A drug is said to have _____ pharmacokinetics if the rate of elimination is estimated by percent per unit of time
Linear (regardless of the concentration, a percent of remaining drug is eliminated, e.g. half lives)
If a patient's total serum concentration of a drug is 100 mg/L and their free concentration is 8 mg/L, how protein bound is this drug?
About 92% protein bound
4-5 half lives (some sources say 3, so I'll accept 3-4 or 3-5 as well)
Renal dose adjustments for medications are commonly made using creatinine clearance as an estimate for renal function. Please tell me (or write on the board) the Cockcroft-gault equation for estimating CrCL.
What is (((140-age) x wt)/ (72 x serum creatinine) ) x 0.85 if female)
A patient with obesity may have increased drug clearance due to ________.
Increase renal size
A drug with _____ kinetics, may exhibit psuedo first order (or linear kinetics) until enzymes responsible for metabolism are saturated.
What is zero order or nonlinear kinetics
A patient had a phenytoin serum level of 10 mg/L on his regimen of 300 mg daily. The physician wanted a target serum concentration closer to 20 mg/L and the daily dose was doubled. Why is this a correct or incorrect approach?
What is incorrect and what is phenytoin has zero-order kinetics
Cmax after an initial bolus dose can be estimated using this equation.
C = Dose/Vd
Extremes of weight, diet (excessive protein intake or poor diet), frail elderly patients, unstable renal function, drug interactions
Neonates often have altered clearance. Please explain at least one reason neonates have clearance rates that are different than adults
What is reduced renal function, what is higher volume of distribution, what is differences in bioavailability, what is differences in CYP enzyme activity
If a patient's phenobarbital level, drawn at steady-state) is 10 mg/L, and he is taking 90 mg BID. How much do you need to increase the total daily dose to reach a serum level of 20 mg/L?
How much is 180 mg BID (or 360 mg TDD is also acceptable)
Typical goal phenytoin serum levels are 10-20 mg/L with an estimated fraction unbound of 0.1, thus goal free-phenytoin levels are 1-2 mg/L. If a patient has a fraction unbound of 0.2 and a total serum level of 20 mg/L, what is his free phenytoin level?
4 mg/L
If a patient's serum level is 15 mg/L after a bolus of 1000 mg and our target serum level is 20 mg/L. What incremental load (or mini-load) can be given to rapidly achieve the therapeutic concentration?
About 335 mg (may vary slightly depending on how you rounded your decimal points) or if you solved via proportion, 333 mg.
About 110 mg q 12 hours