What can happen if you take expired penicillin?

1) Prescription medicine should be taken under doctor supervision as drug interactions or allergic reactions are possible.

2) It is likely that if you have old penicillin that you did not take the full course when it was prescribed earlier and this means you would most likely not have enough for a full course now.

3) Improper use of antibiotics can be harmful because overuse of anything can be toxic. Some drugs pose dangers to your kidneys or other organs.

4) Antibiotics also have the potential to disrupt the natural flora in your body. You need to have bacteria in your digestive tract to survive; killing it would be bad.

5) There is some validity to the claim that once the seal on a bottle of prescription drugs is broken, and the drug is exposed to an unpredictable environment, there is no certainty regarding the effectiveness of the drug.

The Food and Drug Administration, in conjunction with the Department of Defense did a study called the Shelf Life Extension Program (SLEP), which indicated that while some antibiotics lose some potency over long periods of time, most were largely effective longer than indicated on labels.