The selected antibiotic should beused in right dose, right route, and right time and for right duration. Theabove approach is known as Rational antibiotic therapy. It makes antibioticmaximally effective and reduces the development of bacterial resistance.1.
For an antibioticto maximally effective, the plasma concentration must be high so as to allowdiffusion into the tissue contaminated by the bacteria. To achieve thispreoperative prophylactic antibiotic should be given twice the usualtherapeutic dose.2. Correct time ofadministration of antibiotics is considered. To be maximally effectiveantibiotic should be in the tissue at the time of contamination occurs. As ageneral guideline antibiotics should not be given on the previous day nor inthe patient’s room before arrival in the operating room.
The antibiotic shouldbe administered intravenously/ intramuscularly 30 minute before the placementof incision at twice the therapeutic dose. For penicillin the dose is 2 millionunits and for cefazolin it is 1g. This dose adequately provides coverage for upto 4 hours (As a general rule prophylactic antibiotic dosage interval should beone half of the usual therapeutic interval). So if the procedure is prolonged,however it is advisable to administer additional doses every 4 hours until thesurgery is completed.3. In patients whoare medically compromised it may be advisable to continue prophylactic oralantibiotics until biologic sealing of the wound has occurred.
4. Use the shortesteffective antibiotic exposure. Continuing antibiotic administration aftersurgery does not decrease the incidence of wound infection.
For short procedurea single dose of antibiotic preoperatively is sufficient to prevent woundcontamination. For longer procedures intraoperative doses are given asnecessary, and a final dose in the recovery room is sufficient to controlinfection. The new approach will reduce the toxicity, allergy, and suprainfection and overall decrease in the use of antibiotic and expense. Usuallyantibiotics that have little or no toxicity like Penicillin, and cephalosporinsare used. There has been occasional report of pseudomembraneous colitisassociated with prophylactic use of ampicillin, the cephalosporins andclindamycin.