The long-term safety and therapeutic response of sodium oxybate ( SXB ) in fibromyalgia syndrome ( FM ) patients were assessed for a combined period of up to 1 year in a prospective , multicenter , open-label , extension study in patients completing 1 of 2 phase 3 randomized , double-blind , controlled , 14-week trials that examined the efficacy and safety of SXB 4.5 g , SXB 6 g , and placebo for treatment of FM .