TABLE 1.

The penicillins; their chemical groups and subtle differences in modes of action (MOA) against bacterial cell wall biosynthesis (Patrick, 2013).

β-lactam penicillins, COR-substituted 6-aminopenicillanic acid (acyl derivatives of 6-APA)
Sub-group	Benzylpenicillin	Aminopenicillins	Carboxypenicillins	Ureidopenicillins	Acid-resistant	Penicillinase-resistant	Penicillin prodrug
Sub-structure	6-benzyl substituted	6-amino substituted	α-carboxy substituted	α-urea substituted	6-electron withdrawal substituted	6-steric shield substituted	Ampicillin esters of carboxyl moiety
MOA	Cell wall, inhibition of transpeptidase enzyme
Sub-MOA	Lipophilic, but unstable in stomach acid	Broad spectrum, higher hydrophilicity, crosses Gram-negative cell wall			Stable in stomach acid	Blocks β-lactamase	Ampicillin has poor absorption, esters aid absorption and are hydrolyzed in phase-1 metabolism
Inhibition	Bactericidal
Examples	Penicillin G	Ampicillin, Amoxicillin, Penicillin N, Penicillin T	Carbenicillin, carfecillin (prodrug), ticarcillin	Azlocillin, mezlocillin, piperacillin	Penicillin V, ampicillin, amoxicillin	Methicillin, nafcillin, temocillin, oxacillin, cloxacillin, flucloxacillin, dicloxacillin	Pivampicillin, talampicillin, bacampicillin