It's interesting that you post this question. I don't think the antibiotics cause nightmares but the last two times that I took antibiotics (including this afternoon), I took a nap and had a horrible nightmare.

I'm wondering why too, hopefully you'll get some worthy answers that can explain this.

I'm sure any chemical can induce side effects on certain individuals.

No I dont think that is one of the side effects of them. Best to call your doc. or pharmacy.

I know that sleeping pills can.
I know quite a few people who get night terrors.
Not sure about antibiotics however.

As a doctor explained it to me, the antibiotics are probably helping you sleep longer and deeper so you tend to remember your dreams more often. As to what usually causes nightmares, they usually occur when a person has anxiety, feels insecure, guilt or depression. And usually when we're sick, we do feel anxious and insecure. My best nightmares have happen when I've been sick. With or without medication. Sort of why people have nightmares when taking sleeping pills.