Lizbeth,
N-Acetlyl Cysteine (NAC) 600mgs. 3 times daily (1 with each meal) I have a doctor friend who recommends many supplements to be taken 3 weeks on and one week off, or 3 times a week to protect the liver. But I take it every day. But I thought I'd mention the caution to you. I get it on line at Vitacost, using their own brand NSI, plus always use a 5% discount code that can be googled. I have also purchased it The Vitamin Shoppe.