Antibiotics can be classified in several ways. The most common method classifies them according to their action against the infecting organism. Some antibiotics attack the cell wall; some disrupt the cell membrane; and the majority inhibit the synthesis of nucleic acids and proteins, the substances that make up the bacterial cell. Another method classifies antibiotics according to which particular bacterial strains they affect: staphylococcus, streptococcus, or Escherichia coli, for example. Antibiotics are also classified on the basis of their chemical structure, as penicillins, cephalosporins, aminoglycosides, tetracyclines, macrolides, or sulfonamides, among others. Penicillins are bactericidal, inhibiting formation of the cell wall. There are four types of penicillins. Penicillin-G types are effective against gram-positive strains of streptococci, staphylococci, and some gram-negative bacteria. Ampicillin and amoxicillin have a range of effectiveness similar to that of penicillin-G, with a slightly broader spectrum, including some gram-negative bacteria.
Side effects of the penicillins, while relatively rare, can include immediate and delayed allergic reactions—specifically, skin rashes, fever, and anaphylactic shock, which can be fatal.
Penicillin G, cloxacillin, ampicillin, amoxicillin.