Hi, Soccertese,
I know this reply is a bit late in coming, but I had the same experience with atenolol several years ago. Since I'd been taking that particular beta blocker for a few years without incident, it surprised me when I began to have disturbing symptoms, including chest discomfort. These symptoms began to occur after my pharmacist gave me a generic brand of atenolol, whereas up to that time I'd been taking what I seem to recall was the brand-name version of the drug.

When I looked closely at the new pills I realized something looked different. Some of the pills were jagged around the edges. The markings on the pills seemed blurred or indistinct, if you know what I mean. Just to be certain I wasn't imagining things, I took another one the following day. The same adverse effects occurred, the most troubling of which was chest pain. I began to suspect these pills were counterfeits.

I took the pills back to the pharmacist, told him what I'd been experiencing, and questioned the legitimacy of the pill manufacturer. (I cannot recall the name of the drug maker, but it was located somewhere in India.)

As you might expect, the pharmacist told me that they were generic, and generics were the same as the brand name, blah, blah, and that maybe I was allergic to some of the "fillers" in the pill. I informed him that chest pain was not, to my knowledge, a common side effect of the fillers used in pharmaceuticals. He proceeded to argue with me. Needless to say, I never went back to that pharmacy, my doctor wrote me another prescription for the real thing, and I never had the problem again.

If you still have the pills take a look at them; inspect some of the pills, particularly the shape and markings on each pill. It sounds as though you may have inadvertently gotten some pills of questionable origin and quality. As the other poster said, chest pain is not usually a side effect of atenolol, particularly in a dose as low as 25 mg. Good luck in resolving this situation.