Injection Gentamicin works best against aerobic gram-negative rods. Infections brought on by gram-positive bacteria are also treated with gentamicin in combination with other medicines. It acts by preventing bacterial development. As prescribed by your doctor, this drug is injected into a vein or muscle once every eight hours. Apart from this, Injection Gentamicin is used to treat many different bacterial infections. The dosage is determined by your weight, medical history, and treatment response. This is very effective as well as economical to use.