Non-linear PK

Question 1

Define non-linear PK

Answer 1

Where drug exposure changes disproportionately with dose

Question 2

Which PK processes can become saturated?

Answer 2

Any that involve a protein to move the drug across the membrane or an enzyme for metabolism. E.g. absorption, distribution, metabolism, excretion

Question 3

If you normalise for dose of two concentration- time profiles (2 different doses of same drug) and the resultant lines are superimposable, is the PK of the drug linear or non-linear?

Answer 3

Linear

Question 4

Why might lower doses of a non-linear drug appear linear (pseudolinear) on the concentration - time profile?

Answer 4

Because the proteins are not yet saturated at these low doses

Question 5

Which excretion mechanism is saturatable?

Answer 5

Renal tubular secretion