Omnipen is part of the Penicillin Antibiotics class and treats Meningitis, Bacterial Infection, Upper Respiratory Infection and other conditions. Penicillin antibiotics are used to treat treat urinary tract infections, upper respiratory tract infections, lower respiratory infections, skin infections, bacterial infections, gastrointestinal infections, meningitis, and pneumonia. They work by killing the bacteria that is causing the infection. Omnipen is only available as a brand name drug.