antibioticsbooks

54 PART 2 Antibacterial Drugs
Spectrum
Good: Treponema pallidum, most streptococci,
including Streptococcus pneumoniae
Moderate: enterococci
Poor: almost everything else
Adverse Effects
Similar to those of other beta-lactams.
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Important Facts
• Natural penicillins have a very short half-life
and must be dosed frequently or given by continuous
infusion. Long-acting depot formulations
(procaine, benzathine) are available for
intramuscular administration. It is important
to know the differences among these formulations
because the doses vary considerably. It
is even more important not to give procaine or
benzathine products intravenously, which can
be fatal.
• Penicillin V is the oral form of penicillin G.
Other drugs have supplanted it in most, but
not all, uses.
• Penicillin G remains the drug of choice for
syphilis.
• Because of resistance, penicillin is a poor
empiric choice for most infections. Not all textbooks
and references have been updated to
reflect the changes in penicillin use that have
resulted from widespread resistance.
• The intravenous penicillin breakpoint for
Streptococcus pneumoniae were recently
redefined, which lowered the percentage of
S. pneumoniae isolates considered resistant to