Currently taking 300mg of quetiapine extended release alongside mirtazapine 45mg for depression. Not really feeling the combination is working and making little difference. Does anyone know or have experience as to whether there is any difference to the effectiveness between quetiapine extended release and the instant release? When I first started the quetiapine I was given the option of the extended release and instant release and my psychiatrist said the only difference being instant release making you more sleepy, as mirtazapine helps on the sleep front I opted for the extended release. Feeling pretty desperate on the depression front and now wondering if I made the right choice, or if the instant release is more effective.