Gentamicin and penicillin can be used together, but when used together should follow the doctor’s advice. Gentamicin belongs to aminoglycoside antibiotics, can be combined with bacterial ribosomal 30s subunit to block bacterial protein synthesis, used for bacteriostatic inhibition of bacterial resting, and its main gram-negative bacilli have antibacterial activity; and penicillin belongs to the β-lactam antibiotics, which can destroy the bacterial cell wall, in the process of bacterial reproduction to play a role of bacteria, and its main gram-positive coccobacilli have antibacterial activity. Both drugs belong to antibiotics, but the two antibacterial spectrum is different, used together can play a synergistic effect to increase the antibacterial effect. So gentamicin and penicillin can be used together. Clinically gentamicin is used for the treatment of enteritis and other intestinal infectious diseases caused by sensitive bacteria, and is also used in the preparation of colon surgery. Penicillin is used to treat mild to moderate infections caused by penicillin-sensitive bacteria, as well as soft tissue skin infections caused by sensitive staphylococci. Adverse reactions such as loss of appetite, nausea, and diarrhea have been reported with gentamicin; nausea, vomiting, upper abdominal discomfort, and diarrhea have been reported with penicillin. Gentamicin is contraindicated for those who are allergic to aminoglycoside antibiotics; penicillin is contraindicated for those who have positive skin test reactions, those who are allergic to other penicillins, and those with infectious mononucleosis. If you need to use the drug, it should be used under the guidance of a physician, not self-medication to avoid adverse reactions.