Types of antibiotics There are hundreds of different types of antibiotics, but most can be divided into six groups. Penicillin (such as penicillin and amoxicillin)-used widely to treat a variety of infections, including skin infections, lung infections, and urinary tract infections Cephalosporins (such as cefotaxime)-used to treat a wide range of infections, but some are also effective for more serious infections, such as sepsis and meningitis Aminoglycosides (such as gentamicin and tobramycin)-used only in hospitals to treat very serious illnesses, such as sepsis, because they can cause serious side effects, including hearing loss (e.g., gentamicin and tobramycin)-used only in hospitals to treat very serious conditions, such as sepsis, because they can cause serious side effects, including hearing loss and kidney damage; they are usually given by injection, but may be given as drops for some ear or eye infections Tetracyclines (e.g., tetracycline and doxycycline)-can be used to treat a variety of infections, but are usually used to treat skin conditions such as acne. Macrolides (e.g., erythromycin and clarithromycin)-particularly effective in treating lung and chest infections, in people who are allergic to penicillin, or in strains of bacteria that are resistant to penicillin. Fluoroquinolones (e.g., ciprofloxacin and levofloxacin) are broad-spectrum antibiotics that have been used to treat a variety of infections, especially respiratory and urinary tract infections. Due to the risk of serious side effects, these antibiotics are no longer routinely used. Precautions Some antibiotics are not suitable for people with certain medical problems and for pregnant and breastfeeding women, and should be taken as prescribed by a doctor. Some antibiotics should not be mixed with other medications, such as birth control pills and alcohol.