Can I use the quasi-equilibrium approximation when drug and ligand distribution volumes are different?

A drug $D$ binds a ligand $L$ to form a complex $C$ according to the law of mass action. Furthermore, mass balance should be achieved. Can I still assume quasi-equilibrium when the distribution volumes of the drug and the ligand are different?


From the quasi-equilibrium approximation it follows that


$$k\_\mathrm{on} [D] [L]=k\_\mathrm{off} [C],$$


from which the dissociation constant is


$$K\_\mathrm{d} = \frac{[D][L]}{[C]} = \frac{\frac{D}{V\_D}\frac{L}{V\_L}}{\frac{C}{V\_C}},$$


with $[x]$ describing the concentrations, $x$ the amounts, and $V\_x$ the distribution volumes.


Mass balance now means that


\begin{align}
D\_\mathrm{tot} &= D + C &
\text{and}&&
L\_\mathrm{tot} &= L + C.
\end{align}


Can I now rewrite the equation for $K\_\mathrm{d}$ as


$$K\_\mathrm{d} = \frac{\frac{D\_\mathrm{tot}-C}{V\_D}\frac{L\_\mathrm{tot}-C}{V\_L}}{\frac{C}{V\_C}} ?$$


Even though this might be very basic, I would really appreciate if someone could explain it in detail.


