Class	Drug	Antimicrobial spectrum
Natural penicillin	Penicillin V	Streptococcus species and oral cavity anaerobes
Penicillinase-resistant penicillin	Cloxacillin (Tegopen)	Methicillin-sensitive Staphylococcus aureus and Streptococcus species
	Dicloxacillin (Dynapen)
	Nafcillin (Unipen)*
	Oxacillin (Prostaphlin)*
Aminopenicillin	Amoxicillin	Same coverage as penicillin V, plus Listeria monocytogenes, Enterococcus species, Proteus mirabilis and some strains of Escherichia coli
	Ampicillin
	Bacampicillin (Spectrobid)
Beta-lactam–beta-lactamase inhibitor combination	Amoxicillin-clavulanate (Augmentin)	Same coverage as aminopenicillins, plus betalactamase–producing strains of methicillin-sensitive S. aureus, Haemophilus influenzae and Moraxella (formerly Branhamella) catarrhalis
Antipseudomonal penicillin	Carbenicillin (Geocillin)	Limited activity against Pseudomonas and Klebsiella species
First-generation cephalosporin	Cefadroxil (Duricef)	Improved coverage of methicillin-sensitive S. aureus, E. coli, P. mirabilis and Klebsiella species
	Cephalexin (Keflex)
	Cephradine (Velosef)
Second-generation cephalosporin	Cefaclor (Ceclor, Ceclor CD)	Compared with first-generation agents, better coverage of beta-lactamase–producing organisms
	Cefprozil (Cefzil)	such as methicillin-sensitive S. aureus, H. influenzae,
	Cefuroxime axetil (Ceftin)	M. catarrhalis, E. coli, P. mirabilis and Klebsiella species
Carbacephem	Loracarbef (Lorabid)	Same coverage as second-generation cephalosporins
Third-generation cephalosporin	Cefdinir (Omnicef)	Variable loss of Staphylococcus and Pneumococcus coverage; compared with second-generation cephalosporins, somewhat expanded coverage of gram-negative organisms; enhanced coverage of Proteus vulgaris and Providencia species
	Cefixime (Suprax)
	Cefpodoxime (Vantin)
	Ceftibuten (Cedax)