antibioticsbooks

chapter 5 Adverse Consequences 45
Use the Most Narrow-Spectrum Agent Appropriate
for the Patient’s Infection
Broader-spectrum agents multiply the number
of bacteria affected by the drug, increasing the
chances both for development of resistance and
superinfection. “Broader” and “newer” are not
synonymous with “better”: for example, good old
penicillin kills susceptible organisms more rapidly
than almost any drug on the market. The treating
clinician’s goal always should be definitive, narrowspectrum
therapy.
Use the Proper Dose
Bacteria that are exposed to low concentrations
of antibiotics are more likely to become resistant
than those exposed to effective doses. After all,
dead bugs don’t mutate! Further research in pharmacodynamics
should make it easier to determine
the proper dose for each patient and thus to reduce
the likelihood that resistance will develop.
Use the Shortest Effective Duration of Therapy
Unfortunately, duration of therapy is one of
the least-studied areas of infectious diseases.
Examination of standard treatment durations
says much more about how humans think than
about how antibiotics and bacteria truly interact—
durations are typically 5, 7, 10, or 14 days, more in
line with our decimal system and the days in a week
than with anything studied precisely. New studies
are showing that shorter durations of therapy are
often just as effective as prolonged courses and
possibly less likely to select for resistance. As studies
progress and determine additional factors that