It's perfectly safe. You've got to watch out for those blanket lists of side effects you find on sites like WebMD. Those lists are just lists of everything any patient ever reported and generally they don't show you how common it is. Millions of people with afib have taken millions of doses of amoxicillin without a problem (including me) and then one guy comes along who thinks it caused his afib and now it's listed. If it did cause an arrhythmia, it was probably part of an allergic reaction so shouldn't have been listed at all. This is what makes those lists nearly useless.
It won't trigger your afib, and your sinus infection isn't getting better without it.
