This is not a new side effect, but I wanted to let other people who are taking Flagyl to hear this and hope it will help them while they are taking this awful medication. The pill form is the worst medication I have ever had to swallow. I found that if I coat the pill in butter, I can swallow the pill without gagging and I have no aftertaste. I also eat a couple of crackers before I take it, to stop the stomach upset.