Red/gray pill. Oblong like capsule but not an actual capsule. It's broke in half with just the red side and very little of the gray side. The red side has imprint in black either the letter "O" or the number "0". Any ideas? ## Hi Scias, Unfortunately, since the entire pill isn't showing.. neither is the imprint which is vital to verifying the pill's identity. I found a number of red/grey capsules with an imprint including the letter O. One of the capsules I located is, Principen which contains (500 mg) of ampicillin. It is a red/grey capsule with the imprint BRISTOL 7993 (in black letters) on each side. Manufacturer: Bristol-Myers Squibb Ampicillin is closely related to amoxicillin, another type of penicillin, and both are used to treat urinary tract infectio...