I am often asked the about the difference between a medication such as Nystatin and a medication such as Diflucan and their effects on yeast and what are some of the things you need to be aware of when using these medications. Both Nystatin and Diflucan are considered antifungals which mean they have an eradication or inhibiting or killing effect against yeast organisms, specifically candida.  We know that candida is a big problem for many kids on the spectrum. We commonly treat using Nystatin and/or Diflucan to lower the levels of candida to bring on improvement in behavior. We know yeast can increase stimming behaviors, silly, goofy and giddy behaviors, and other negative behaviors. Nystatin is considered a local antifungal.  It inhibits the overgrowth of colonies of yeast that line the digestive system. There is no significant absorption of Nystatin into the bloodstream so it can be taken long term with no major concern.  It can be taken for months or years in many cases. Think of Nystatin like Pepto Bismal, Pepto Bismal coats the stomach and Nystatin coats the inner lining of the digestive tract.  Because it coats the lining of the digestive tract, generally we need to take it several times a day to keep that coat in place.  So, 3, 4 or even 5 times a day is ideal, even though that is difficult to do. Minimally 3 times per day, preferably 4 and Nystatin becomes quite effective. In comparison, Diflucan is considered a systemic antifungal which means when you take it orally it will be absorbed into the blood stream within about 2 hours. It also has a local effect in the digestive system as well but it is absorbed into the body and is metabolized in the liver. So there is the potential for risk of liver stress with long term use.  So if your child is taking Diflucan you will want to run blood work every 6 – 8 weeks in my experience to check for liver stress.  What you can do with Diflucan is you  can take it for a short time like 2 weeks, 3 weeks or 4 weeks and then take a couple week break and cycle back to it and in many cases that works well. There are other medications that fall into the same category as Diflucan called Nizoral, Lamisil and Sporonox. The primary ones I use in my practice are Diflucan and Nizoral and both are systemic and so with use over a prolonged period of time, you do need to check liver enzymes function. Nystatin really doesn’t need to have the liver function tests because it just stays in the GI tract.  As a recap, both Nystatin and Diflucan are antifungal medications. Nystatin has a local effect with minimal systemic absorption, if at all. Diflucan is a systemic antifungal so you do need to do liver tests to check for liver function periodically.