Im on zoloft 100mg and buspar (buspirone) 10mg once morning can i take remeron at nigth 15mg?

Talk to your doctor: and/or your pharmacist. Presumably the same doctor is prescribing all your medications. If not, they all need to know what you are being prescribed so that you can safely take what they are recommending for you. Remeron (mirtazapine) is commonly used on the meds you are taking, but without knowing your full history, other meds etc., I cannot tell you it's safe or not. Talk to your prescriber(s) & pharmacist.

Depression, Anxiety: Zoloft (sertraline) is a medication for Depression and Anxiety Zoloft (sertraline) 100mg/day is high as maintenance dose for depression; it can cause Insomnia, anxiety, vivid dreams and depression. Buspar is a medication for Anxiety, It can cause anxiety and vivid dreams. Remeron is a medication for depression and can cause sleepiness and abnormal dreams. See a Psychiatrist for diagnosis, Therapy, Yoga and Meditation.