(2) These penicillins are all excreted via the kidneys, with the exception of
nafcillin, which is excreted via the biliary canal.
(3) This class is to be used when staphylococcal beta-lactamase infection is
known or suspected. The organism in this case is S. aureus. Seventy percent of all
community acquired staphylococcal infections are beta lactamase producing.
(4) Adverse reactions, cautions, and warnings for these drugs are the same
as those for the natural penicillins. Some hepatotoxicity can be produced as noted by
transient high levels of SGOT, SGPT, and LDH, especially with the use of oxacillin.
These penicillins are available in the following preparations:
(a) Methicillin Na (Staphcillin).
(b) Nafcillin Na (Unipen).
Oxacillin Na (Prostaphlin).
(d) Cloxacillin Na (Tegopen).
(e) Dicloxacillin Na (Dynapen).
c. Broad-Spectrum Penicillins.
(1) Drugs belonging to this class are natural penicillins that have been
chemically modified. They are very similar to the natural penicillins in their method of
action, metabolism and excretion, reaction, cautions, and warnings.
(2) These drugs are employed against the same microbes as the natural
penicillins, but also have an increased chemical activity against Proteus mirabilis,
Haemophilus influenzae, and E. coli.
(3) Resistance to these drugs is acquired by the gram-negative organisms.
Additionally, the drugs are inactivated by beta-lactamase.
(4) These drugs are used for soft tissue infections, such as the respiratory,
urinary, and gastrointestinal tract as well as otitis media infections. Some authorities
consider them the drug of first choice in the treatment of uncomplicated gonorrhea.
(5) Broad-spectrum penicillins are ampicillin, which is indicated for both
parenteral and oral use, and amoxicillin, which is for oral use only.