Hi and thanks for answering the question .i want to tell you that NEOMYCIN and penicillin are different with each other Both are antibiotics but different composition so they can t be inter- related. And some side effect s are : clumsiness diarrhea difficulty in breathing dizziness drowsiness greatly decreased frequency of urination or amount of urine increased amount of gas increased thirst light-colored, frothy, fatty-appearing stools ringing or buzzing or a feeling of fullness in the ears skin rash unsteadiness weakness side effects may go away during treatment as your body adjusts to the medicine. Thanks