Clinical Pharmacokinetics

Question 1

Define MEC, MTC and the therapeutic range

Answer 1

MEC - where we expect to see an effect (around where the curve takes off) lowest [drug] to produce effect

MTC - where we see toxic effects

Therapeutic Range - [ ] in between MTC and MEC

Question 2

Define and apply the concepts of clearance and half-life to drug dosing

Answer 2

T (1/2) is the time required for the concentration of the drug to decrease by 50 % (expressed in units of time)
Takes ~ 5 half lives for drug to be completely eliminated from body

Question 3

Dose Equation?

Answer 3

Dose = Vd/C

Question 4

Describe repeat dosing

Answer 4

Max and min [] fluxuate b/w doses, there is an accumulation of drug if we assume some still remains.

Question 5

Describe steady state

Answer 5

Rate of drug administration = rate of drug elimination (~5 half lives)

Can be reached passively 5 half lives or actively with loading dose

Question 6

What is the passive approach to reaching steady state?

Answer 6

Give small repeat doses at regular intervals (often drug’s half life) to reach therapeutic range

Question 7

What is the active approach to reaching steady state?

Answer 7

Loading dose = ctarget * Vd

Maintenance Dose (MD)

The LD must be followed by MD to maintain steady state.

The MD must replace the amount of drug eliminated from the body in b.w. doses (this will be smaller than LD)

Question 8

Describe the Therapeutic Drug Monitoring approach

Answer 8

Provides individualized dosing information.
Useful for drugs with a narrow TI and for special populations
Give the initial dose based on standard doses
-> measure the person’s actual plasma concentration
->revise subsequent dosing and make sure it falls within therapeutic range.

Dose new/dose previous = [] ss target/ [] ss measured