Antibiotics are of the oldest discovered drugs that combat specific microorganisms like bacteria and fungi. The antibiotics are classified according to three criteria and although that each category contains several drugs but each one of them is unique in some features and effects.

The first classification is according to the spectrum. The spectrum means the number of the organisms affected by the same drug. There are narrow and wide spectrum antibiotics. The wide spectrum antibiotics affect several types of bacteria and fungi and it is usually used where the specific type of the microorganism is unknown. For example, when we are treating an bacterial caused inflammation, we know that we are dealing with a staphylococcus or streptococcus microorganism so the doctor can proceed with the treatment without asking for more lab tests to identify the specific type of the microorganism using the broad spectrum antibiotics but in other cases, where we know the specific type of the microorganism, we can use the narrow spectrum antibiotics that are more effective on specific microorganism but less effective on others.

The second classification is according to the type of the action of antibiotics. It could be bactericidal or bacteriostatic. The bactericidal antibiotics kill the harmful microorganism while the baceriostatic ones tend to slow down their growth and give the body the chance to use its immune system against the microorganisms. In case of virulent microorganisms or in case of weak immunity, bactericidal antibiotics are preferred because they will omit the problem from its roots but they will affect the normal microorganisms in the body. In mild cases, bacteriostatic antibiotics could be used because of their minor side effects.

The third classification of antibiotics is according to the route of administration of the drug. The prevalent route of administration is the oral route but, there are other routes of administration that are more effective in certain cases like injection or topical applications.

Antibiotic injection is used when the doctor wants to see a rapid onset of action and a quick presence of antibiotic in the blood stream. It is used in severe cases and as a post operative regime. Topical application of antibiotics is more used in cases of superficial inflammations and skin infections. Direct application of antibiotics on the affected part make it more powerful in combating the microorganism because when antibiotic is administered through oral or injection route, some of it is degraded in the liver before it reach the peripheral circulation and superficial legions.