The possibility of CoO(OH) use as an electrode modifier for isoniazid electrochemical detection has been evaluated from theoretical point of view. The corresponding mathematical model for the system was analyzed by linear stability theory and bifurcation analysis. It was shown, that CoO(OH) may be used as an electrode modifier for isoniazid electrochemical detection in lightly and moderately alkaline solutions. The steady-state is easy to maintain, and the electroanalytical process is efficient. The process is diffusion controlled. The electrochemical instabilities was also evaluated