### Scheme or diagram

The scheme is then:-

**Diagram V-1, Scheme for drug excreted into urine, one compartment**

### Differential equation

Since the rate of elimination from plasma is the same as the rate of appearance of drug into urine.

**Equation V-1. Differential Equation for Cumulative amount Excreted**

Since according to this model, the drug is either in the body or has been eliminated into urine.