Medications and food last longer in a dark, cool, dry environment. If they are kept in a warm area, or in a humid area, or they are in a brightly lit room or exposed to sunlight, they break down very quickly.
Always use anti-biotics before they expire.
If you have unwanted or expired medications, take them to a chemist/ pharmacy and ask them to dispose of the products. They have companies that take expired and unwanted drugs and dispose of them safely.
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You should not be stock piling anti-biotics.
API General Cure contains Praziquantel (tapeworm treatment) and an anti-biotic called Metronidazole, and that should only be used for known bacterial infections that have not responded to normal medications.
Improper use and mis-use of anti-biotics has lead to drug resistant bacteria that kill people, birds, reptiles, animals and fish.