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The first antibiotic to be discovered was penicillin, a natural
product of Penicillium mold. Innumerable microbial products have
been investigated since then, and much work has been done in chemically
modifying these natural products in an attempt to enhance the benefits
while minimizing the undesirable effects. These modified products, termed
semisynthetic antibiotics, increased stability and solubility, improved
pharmacokinetics (ie, wider distribution and longer half-life),
and increased antimicrobial activity. Minimizing the undesirable
effects creates antibiotics with decreased toxicity and increased
efficacy.
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Unfortunately, overuse of this vast array of antibiotics now
is one of our most pressing problems. Antibiotics are the most commonly prescribed
class of drugs in the United States. In children, antibiotics represent
about 30% of all prescribed drugs. Almost half of children under
age 15 will have an antibiotic prescribed to them each year.1
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Misuse of antibiotics is common. Thirty percent to 65% of
antibiotic prescriptions in hospitals are found to be irrational,
inappropriate, or of questionable value. In community practice,
market research data have determined that 50% of physicians
prescribe antibiotics for the common cold, although this trend has
improved in recent years.1,2 The reasons for this
antibiotic “abuse” are multifactorial, but the
desire to help patients, fear of missing a bacterial infection that
might respond to antibiotics, and the ease of treating a possible
bacterial infection versus considering and investigating an alternative
diagnosis all contribute.
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One prevalent attitude is that the risk of not treating an infection
is greater than the risk of side effects from antibiotic treatment.
In fact, approximately 5% of patients taking antibiotics
experience side effects, and the indiscriminate use of antibiotics
alters the drug-resistance patterns of isolates from the individual
being treated and from the environment in general. Furthermore,
a potentially more serious infection such as meningitis can be masked
by incidental antibiotic therapy.
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The decision to prescribe an antibiotic is based on proof or
strong suspicion that the patient has a bacterial infection. Probable
viral infectious or noninfectious processes should not be treated with
antibiotics. However, in the critically ill patient in whom there
is some chance that a bacterial infection may be a contributing
factor, it is prudent to administer antibiotics effective against
the most likely pathogens.3
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Whenever possible, antibiotic selection should be based on the
isolation of a pathogen, but most patients who require antibiotic
therapy present with an acute problem that mandates initial empiric
therapy. The antibiotic(s) chosen should be based on the pathogens
likely to be responsible for the infection, knowledge of local antibiotic
sensitivity patterns, and specific host characteristics. If more
than one antibiotic is active against the likely pathogens at the
site of infection, the specific agent should be chosen on the basis
of relative toxicity, convenience of administration, and cost. Once
the pathogen is identified, the antibiotic with the most narrow spectrum
of activity should be ...