Sepranolone (UC1010) is a GABA-A modulating steroid antagonist (GAMSA) and does not antagonize the effect of GABA itself or other GABAA agonists like benzodiazepines and barbiturates. The interaction of neuroactive steroids (i.e., allopregnanolone and Sepranolone) with GABA-A receptor is particularly important in mood disorders. For example, allopregnanolone administration decreased saccadic eye velocity in healthy female volunteers and induced sedation and these effects were diminished by simultaneous sepranolone administration. Thus, allopregnanolone effects are antagonized by its isomer sepranolone. UC1010 reduces symptom severity and impairment significantly more efficiently than placebo in women with a well-defined, pure premenstrual dysphoric disorder. No severe adverse events were reported during the UC1010 treatment and safety parameters (vital signs and blood chemistry) remained normal during the study. It was revealed also that increases in ring A-reduced progesterone metabolites, particularly Sepranolone, are associated with chronic fatigue syndrome.