I assume you mean NAC, N-acetyl cysteine? You can Google this question. You can ask your pharmacist and prescriber. You don't day why you're taking these two together. You might not get great info from your pharmacist or provider, because they often don't know much about nutrients, but sometimes they do, so ask. You can also ask a manufacturer of NAC. A lot of times, whether two things go together well or not depends on why you're taking them and the state of your health. While most of the action of NAC is as an antioxidant, it does have other effects on the body. I might even affect serotonin somewhat. I only add that because whenever you take anything that affects brain neurotransmitters, and especially two things that affect brain neurotransmitters, there are common things to look out for. Modanfil is obviously going to have more of that possibility, but these are not always easy questions to answer but wise to at least try.