One, bupropion, is an anti depressant that blocks the effects of the neuro transmitter noradrenaline.
People with ptsd already have high levels of noradrenaline.
British Dictionary definitions for noradrenaline
a hormone secreted by the adrenal medulla, increasing blood pressure and heart rate, and by the endings of sympathetic nerves, when it acts as a neurotransmitter both centrally and peripherally. Formula: C8H11NO3US name norepinephrine