The maximally effective antibiotic should be in the tissue

The selected antibiotic should be
used in right dose, right route, and right time and for right duration. The
above approach is known as Rational antibiotic therapy. It makes antibiotic
maximally effective and reduces the development of bacterial resistance.

1.     
For an antibiotic
to maximally effective, the plasma concentration must be high so as to allow
diffusion into the tissue contaminated by the bacteria. To achieve this
preoperative prophylactic antibiotic should be given twice the usual
therapeutic dose.

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2.     
Correct time of
administration of antibiotics is considered. To be maximally effective
antibiotic should be in the tissue at the time of contamination occurs. As a
general guideline antibiotics should not be given on the previous day nor in
the patient’s room before arrival in the operating room. The antibiotic should
be administered intravenously/ intramuscularly 30 minute before the placement
of incision at twice the therapeutic dose. For penicillin the dose is 2 million
units and for cefazolin it is 1g. This dose adequately provides coverage for up
to 4 hours (As a general rule prophylactic antibiotic dosage interval should be
one half of the usual therapeutic interval). So if the procedure is prolonged,
however it is advisable to administer additional doses every 4 hours until the
surgery is completed.

3.     
In patients who
are medically compromised it may be advisable to continue prophylactic oral
antibiotics until biologic sealing of the wound has occurred.

4.     
Use the shortest
effective antibiotic exposure. Continuing antibiotic administration after
surgery does not decrease the incidence of wound infection. For short procedure
a single dose of antibiotic preoperatively is sufficient to prevent wound
contamination. For longer procedures intraoperative doses are given as
necessary, and a final dose in the recovery room is sufficient to control
infection. The new approach will reduce the toxicity, allergy, and supra
infection and overall decrease in the use of antibiotic and expense. Usually
antibiotics that have little or no toxicity like Penicillin, and cephalosporins
are used. There has been occasional report of pseudomembraneous colitis
associated with prophylactic use of ampicillin, the cephalosporins and
clindamycin.