FINAL EXAM- PROF K

hoping for the best

What are the PK differences between single IV bolus and IV infusion? (include Cmax and Tmax)

IV bolus- brief Cmax, Tmax=Cmax

IV infusion- continuous Cmax, Tmax≠Cmax

What is the main advantage of an IV infusion?

the ability to maintain steady-state concentration

What is the abbreviation for each of the following:

1. steady-state plasma concentration

2. infusion rate

3. drug in the body

4. volume of distribution

5. elimination rate constant

1. C_p(ss)

2. K_o

3. D_B

4. V_d

5. K_e

Infusion Rate ____ Elimination Rate

a. >

b. <

c. =

c. = (NOTE: it’s elimination RATE not the elimination rate constant)

Explain the concept of drug accumulation:

• a gradual buildup of drug concentrations with continuous or successive doses.

• the whole time leading up to steady state concentration is know as the drug accumulation phase

What is the relationship between steady state drug concentration (C_p(ss)) and the infusion rate (K_o)?

directly proportional

What is the relationship between steady state drug concentration (C_p(ss)) and Clearance (CL)?

inversely proportional

Be able to know how to apply all the equations given in the powerpoint. WILL NOT HAVE TO MEMORIZE

Calculate the steady-state Cp, if a drug (CL= 3L/h, Vd=40 L) is administered as an IV infusion at a rate of 15 mg/h.

(Equation sheet is attached)

Cpss= 5 mg/L

Phenytoin is administered as an IV infusion at a constant rate of 45 mg/h. Calculate the steady-state Cp. Assume Vd=30 L, Ke=0.1155 h^-1.

(round to the nearest hundredth in mg/L)

12.99 mg/L

Phenytoin is administered as an IV infusion at a constant rate of 45 mg/h. Determine the elimination rate at steady state. Assume Vd=30 L, Ke=0.1155 h^-1.

6 hr

Phenytoin is administered as an IV infusion at a constant rate of 45 mg/h. Calculate the clearance. Assume Vd=30 L, Ke=0.1155 h^-1.

(round to the nearest hundredth in L/h)

CL= 3.46 L/h

The time required to reach steady state depends on the drug’s ________________.

half-life

Which of the following drugs will take the longest to reach steady state?

a. a drug with a half-life of 10 hours

b. a drug with a half-life of 1 hour

c. a drug with a half-life of 30 minutes

d. a drug with a half-life of 5 hours

a. (longer half-life= longer to reach steady state)

How many half-lives does it typically take to reach steady state?

5 half-lives

Which of the following will NOT affect the time it takes to reach steady state?

a. dose

b. Vd

c. clearance

a

How long will it take to reach steady state if the patient has a Ke= 0.1 h^-1 ?

PRACTICE:

An increase in drug dose will not change the time it takes to reach steady-state, but will result in a higher plasma concentration at steady-state.

a. TRUE

b. FALSE

a. (time to steady state is not effected by dose, but CL and Vd)

PRACTICE:

When drug clearance increases (Vd remains unchanged), steady-state plasma concentrations will ________________.

a. increase

b. decrease

b. (bc CL and Cpss are inversely proportional)

PRACTICE:

When drug infusion rate increases (Vd remains unchanged), steady-state plasma concentrations will ________________.

a. increase

b. decrease

a. (infusion rate and Cpss are directly proportional)

My steady-state plasma concentration was measured and found to be 1.4 mg/L, and I had been on an infusion rate of 7.7 mg/h for the past 72 hours. The doctor then says they want to achieve a Cpss of 2 mg/L. What would be my infusion rate to reach that steady-state goal?

The higher the clearance the __________ steady-state concentration.

lower (think: if you get rid of a drug faster, you will have a lower steady state)

The time to reach steady state is _________________ of the infusion rate.

a. dependent

b. independent

b

If 2 people had similar clearance, but one had a Vd of 15L and the other had a Vd of 49L, which of the following WOULD NOT be effected?

a. time to reach SS

b. t1/2

c. Ke

d. steady state plasma concentration

d

What are the drawbacks of IV infusions? How can this be fixed?

takes 5 half-lives to steady state so it is NOT GOOD in a medical emergency. can be fixed with a LOADING DOSE

PRACTICE:

What graph does the following depict?

a. 1 compartment, IV bolus

b. 1 compartment, IV continuous infusion

c. 1 compartment, IV continuous infusion WITH a loading dose

d. 2 compartment, IV bolus

a

PRACTICE:

What graph does the following depict?

a. 1 compartment, IV bolus

b. 1 compartment, IV continuous infusion

c. 1 compartment, IV continuous infusion WITH a loading dose

d. 2 compartment, IV bolus

c

PRACTICE:

What graph does the following depict?

a. 1 compartment, IV bolus

b. 1 compartment, IV continuous infusion

c. 1 compartment, IV continuous infusion WITH a loading dose

d. 2 compartment, IV bolus

b

PRACTICE:

What graph does the following depict?

a. 1 compartment, IV bolus

b. 1 compartment, IV continuous infusion

c. 1 compartment, IV continuous infusion WITH a loading dose

d. 2 compartment, IV bolus

d

What is the principle of superposition?

each subsequent dose additively influences the total plasma concentration

A patient is given vancomycin IV to achieve steady-state peaks and troughs of 10 and 2 mg/L. The patient is estimated to have the following PK parameters: Vd=14.7L and t1/2 = 3h.

If multiple doses are to be given, determine a suitable dose and dosing interval for this patient.

dose= 117.6 mg

tau= 6.97 hr

The ________________________ is the time required for the max conc to decline to the minimum conc.

dosing interval

True or False: tau stands for time.

FALSEEEEE (stands for dosing interval)

A patient is receiving 900mg of sulfamethoxazole IV every 14 hours. At steady-state the max and min plasma conc were 75.6 and 32 mg/L. What is the Vd of the patient?