Question

In the given picture, which kinetic order the graph is following at the marked place?

(a) 1st order kinetics

(b) 2nd order kinetics

(c) Mixed order kinetics

(d) 1st order at higher doses

The question was asked in homework.

This interesting question is from Non Linearity of Drugs in chapter Compartment Modelling, Non Linear Pharmacokinetics, Bioavailability and Bioequivalence of Drug Biotechnology

Answer 1

Right option is (a) 1st order kinetics

For explanation I would say: The plot is of Michaelis-Menten equation –dC/dt = Vmax C/Km+C, Initially the rate increases linearly with concentration thus showing first order kinetics. At lower doses, it follows 1st order kinetics. It becomes mixed order at higher concentration and then reaches maximum Vmax. Beyond this, it proceeds at a constant rate thus following zero order kinetics.