What Are The Side Effects Of Ibuprofen?

Last night i was at home and i took the last two remaining ibuprofen out of the bottle due to the fact i had a headache, but it turns out the two pills i took had something else in the bottle the same color as 200 mg ibuprofen, expect it was oval shaped and had imprints on fornt and back. Could you tell me what i have taking or if it could harm me.