We studied the rotational Brownian motion of magnetic tri-axial ellipsoidal particles (orthotropic particles) suspended in a Newtonian fluid, in the dilute suspension limit, under applied flow and magnetic fields. The algorithm describing the change in the suspension viscosity has been derived from the stochastic angular momentum equation using the fluctuation-dissipation theorem and a quaternion formulation of orientation space. Simulation results will be presented for the response and effective viscosity of dilute suspensions of ellipsoidal particles in constant magnetic fields in quiescent fluids and in simple shear flow fields.