You provide the manufacturer’s recommended dose of an antibiotic, which is 10mg/kg IV for a 100kg patient. You then draw a level 30 minutes after the dose. Assume rapid distribution and neglible clearance/metabolism over the 30minute period between the time of administration and drug level assement.
3. The serum level of this antibiotic returns at 83.3mg/L. What is the volume of distribution of the drug?
A. 1.6 Liters
B. 16 Liters
C. 12 Liters
D. 1.2 Liters
E. 8 Liters
4. Assume the goal therapeutic serum level of a is 120 mg/L. How much more drug do you need to order to attain this level.
A. 60mg
B. 300mg
C. 45 mg
D. 450mg
E. 600mg
5. A patient with chronic kidney disease has a vancomycin serum level drawn that returns at 37mcg/mL. She will require a redose when the level reaches 15mcg/mL. Her half-life has been determined to be 46 hours. How many hours after the initial serum draw will she require a redose.
A. 52 hours
B. 60 hours
C. 67 hours
D. 73 hours
E. 80 hours
To answer question 3, we need to calculate the volume of distribution of the drug. The volume of distribution (Vd) is a pharmacokinetic parameter that describes the apparent space in the body available to contain the drug. We can calculate Vd using the formula:
Vd = (Dose / Initial serum concentration)
In this case, the dose of the antibiotic is 10mg/kg, and the patient weighs 100kg. So the total dose administered is 10mg/kg * 100kg = 1000mg.
The initial serum concentration is given as 83.3mg/L. Plugging these values into the formula:
Vd = (1000mg / 83.3mg/L)
Calculating this, we get:
Vd ≈ 12 Liters
Therefore, the answer to question 3 is option C - 12 Liters.
Moving on to question 4, we need to calculate the additional drug needed to reach the desired therapeutic serum level. The goal therapeutic serum level is given as 120mg/L, and the current serum level is 83.3mg/L. The difference between these two levels represents the additional drug needed.
Additional drug needed = (Desired level - Current level)
Additional drug needed = (120mg/L - 83.3mg/L)
Calculating this, we get:
Additional drug needed ≈ 36.7mg/L
Therefore, the answer to question 4 is option E - 600mg.
Finally, for question 5, we need to determine the time when the patient will require a redose based on the vancomycin serum level and the half-life of the drug. The half-life represents the time it takes for the concentration of a drug to decrease by half.
The patient's serum level of vancomycin is given as 37mcg/mL, and she requires a redose when the level reaches 15mcg/mL. We can determine the time required for the level to decrease based on the half-life of 46 hours.
To calculate the time required, we can use the formula:
Time required = (half-life * log(initial level / target level)) / log(0.5)
Plugging in the values:
Time required = (46 hours * log(37mcg/mL / 15mcg/mL)) / log(0.5)
Calculating this, we get:
Time required ≈ 52 hours
Therefore, the answer to question 5 is option A - 52 hours.