Principle VI: Choose and Prescribe Appropriate Antibiotic

Principle VI: Choose and Prescribe Appropriate Antibiotic 

Choosing the appropriate antibiotic for treating an odontogenic infection must be done carefully. When all factors are weighed, the clinician may decide that no antibiotic is necessary at all, whereas in other situations, broad-spectrum  or even combination antibiotic therapy may be necessary.
A variety of factors pust be considered when  hoosing an antibiotic from the nearly 70 antibiotics currently available. Antibiotics must be viewed as a
double-edged sword. Although appropriate use may resultin dramatic resolution and cure of patients with infeclions, misuse of antibiotics provides little benefit to offset the associated risks and expense of antibiotic administration.  Therefore the following guidelines are. recommended
for consideration when choosing a specific antibiotic. Determine need for antibiotic admlnlstratlon, It isa common misconception that all infections, by definition, require antibiotic administration; this is not necessarily
the case. In some situations antibiotics are not useful and, in fact, may be contraindicated. In making this determination, three factors must be considered: The first factor is the seriousness of the infection when the
patient comes to the dentist. If the infection has modest swelling, has progressed rapidly, or is a diffuse cellulitis, the evidence would support the use of antibiotics in addition to surgical therapy. The second factor is
whether adequate s urgical treatment can be achieved. In many situations extraction of the offending’ tooth may result in rapid resolution, of the infection. However, in other situations, remoqal of the tooth may not be possible. Antibiotic therapy is important to control the infection
so that the tooth can be removed. The third consideration is the state of the patient’s host defenses. A young, healthy- patient may be able to mobilize host defenses and need less antibiotic therapy for resolution of the infection. On the other hand, patients who have any type of decreased host resistance, such as those with evere metabolic disease or those receiving cancer. chemotherapy, may require vigorous antibiotic therapy
for even minor infections. When these three factors are balanced, several definite indications for antibiotic use in dentistry become clear
(Box 15-3). The first and most common indication is thepresence of an acute-onset infection with diffuse swelling  and msderate-to-severe pain. This intccuon xuxuallv in the cellulitis stage, and, with appropriate .anttbtonc tilerapy and treatment of the offending tooth, rapid resolution
is expected. The second indication is almost any type of infection in a patient who is medically compromised. Such patients who have infections df any severity should be ‘considered candidates for antibiotic administration. The third indication for antibjotic therapy {s the presence
of an infection that has progressed to involvement of extra oral fascial spaces. In these situations the infection is aggressive enough to have spread beyond the mouth, indicating that the host defenses are inadequate to contain the infection. The fourth indication is severe pericoronitis,
with tem peratures higher than 100° F, trismus,and some swelling of the lateral ‘aspect of the face, which occurs most commonly around impacted mandibular third molars. Finally, the patient who has osteomyelitis
requires ant abiotic therapy in additionto surgical therapy to achieve resolution of the infection. Based on the same three criteria, antibiotic therapy would not be indicated or is even contraindicated in other situations (Box 15-4). The first is a minor, chronic, well;localized abscess for which an I&D and ‘treatment of , the offending tooth result in rapid resolution, assuming • that the patient’s host defenses are intact and that the
patient has no other compromising conditions. A second, albeit Similar, contraindication is a very well-localized vestibular abscess, with little or no  ‘facial swelling. In t hese situations the tooth can be opened and necroticpulp removed or the tooth extracted and the abscess incised and drained, which will result in rapid resolution in most patients. Third. is a localized alveolar osteitis, or dry socket. Treatment of the dry socket is primarily palliative, and it is not treated as an infection. Fourth,
patients who have mild pericoronitis with minor gingival edema and mild pain do not require antibiotics for resolution of their infection. Irrigation with hydrogen peroxide or chlorhexidine will result in resolution.
In summary, antibiotics  should be used When clear evidenceexists of bacterial invasion into underlying tissues that is greater than the host defenses can, withstand. Patients who have an impaired ability to defend them  selves against infection and patients who have infectionsthat are not amenable to surgical treatment should be considered for antibiotic therapy. Antibiotics should not be used when no evidence of bacterial involvement is found. Antibiotics do not hasten wound healing and do not ‘provide any benefit- for nonbacterial conditions. ‘Patients who have inflammatory pulpitis will have severe

BOX 15-3

Indications for Use of Antibiotics

• Rapidly progressive swelling
• Diffuse swelling ,
• Compromised host defenses
‘. Involvement of fascial spaces.
• Severe pericoronitis
• Osteomyelitis

BOX 15-4

Situations in Which Use of Antibiotics Is Not Necessary

• Chronic weir-localized abscess
• Minor vestibular abscess
• Dry socket
• Mild pericoronitis

pain. but the pain results from local inflammatory reaction within the pulp. not from bacterial infection. These patients should not be given antibiotic therapy. U\(‘ empirical tilewp)’ routinely. Odontogenic infections are caused by a highly predictable group of bacteria. Additionally, the antibiotic sensitivity of these organisms is well known and consistent. As a result the use of C&S testing is not necessary for routine odontogenic infections. The bacteria that cause more than 90% of odontogenic infections
are aerobic streptococci and anaerobic streptococci, peptostreptococci, Prevotella, and Fusobacterium. Many other species of bacteria are also involved, but they appear to be  opportunistic rather .than causative bacteria. Fortunately the antibiotic susceptibility of the causative bacteria is remarkably consistent. The orally administered antiblotics that are
effective against odontogenic infections include penicillin, amoxicillin, clarithromycin, .clindamycin, cefadroxil, metronidazole, and doxycycline (BOX 15-5). These antibiotics are effective against streptococc i(except metronidazole) and oral anaerobes. Several relatively -important variations can be found within the group. (See Appendix IX for detailed description of the various antibiotics.)  ecause the microbiology and antibiotic sensitivity is well known, it is a reasonable therapeut c maneuver to use one of these antibiotics empirically, that is, to give the  ntibiotic with the assumption that an appropriate.drug is being given. The drug of choice is usually pentcilltn. Alter- -native drugs for use in the penicillin-allergic patient are clarithromycin and clindamycin. The cephalosporin cefadroxil is a useful drug when a broader antibacterial . spectrum is necessary. The cephalosporins should be used with caution in penicillin-allergic patients, because they may also be allergic to the cephalosporins. Doxycycline is
another useful alternative, although some strains of bacteria are resistant to the tetracyclines. Metronidazole is useful only against anaerobic bacteria and should be reserved for situations in which only anaerobic bacteria
are suspected (or in combinatiqn with an antibiotic that has antiaerobic activity such as penicillin). It is ‘clear that patients often, if not usually, fail to take the medication in the way in which it was pre- • s cribed. In fact, Socrates in 400 Be cautioned physiciansto be aware that patients will lie about taking the medications prescribed Hard data exist from many studies that demonstrate that patient compliance decreases with increasing num-

BOX 15-5

Effective Orally Administered Antibiotics Useful for Odontogenic Infections

• Penicillin
• Erythromycin
• Clindamycin
• Cefadroxil
• Metronldazole
• T~tracycline

BOX 15-6

Indications for Culture and Antibiotic Sensitivity Testing

Rapidly spreading infection
• Postoperative infection
• ‘Nonresponsive infection
• Recurrent infectl9n
• Compromised host defenses

penicillin will kill streptococci and oral anaerobic bacteria but will have little effect on the staphylococci of the skin” and almost no effect on gastrointesttnal tract bacteria. As a result, penicillin has little or no effect on the gastrointestirial tract and does not expose a multitude of other bacteria to the opporturrity to develop resistance. By contrast, drugs such as tetracycline are broad spectrum antibiotics, inhibiting not only the streptococd and oral anaerobes bat also a variety of gram-negative
rods. Thus when this antibiotic is given, it has an effect on skin and gastrointestinal bacteria that may result in problems caused by alterations of host flora and overgrowth of resistant bacteria. In addition, broad-spectrum antibiotics provide a multitude of bacteria the opportunity
to develop resistance. In summary, antibiotics that have narrow-spectrum
activity against the causative organisms are just as effective as antibiotics’ that have broad-spectrum activity, without the problems of upsetting normal host microflora populations and increasing the chance of- bacterial
resistance. Use antibiotic with lowestincidence of toxicity and side effects. Most antibiotics have a variety of toxicities and side effects that limit their usefulness. These range from mild to so severe that the antibiotic cannot be used in clinical practice. The antibiotics usually used for odontogenic
infections have a surprisingly low incidence of toxicity-related problems: It is important, however, for the clinician to understand” the probable toxicities and side effects of the drugs they use. Allergy is penicillin’s major side effect. Approximately “2% or 3% of the total population is allergic to penicillin. Patients who have allergic reactions to penicillin, as exhibited by hives, itching, or wheezing, should not be given penicillin again. Penicillin does not have other major side effects or toxicities in the normal dose range
used by dentists. Likewise, clarithromycin, erythromycin, and  .c1indamycin have a low incidence of.toxiciry and side  effects. Clindamycin may cause a severe diarrhea state called pseudomembranous colitis. Several other drugs, such as ampicillin and the oral cephalosporins, also cause this problem. The elimination of much of the anaerobic gut . flora allows the overgrowth of an antibiotic-resistant bacteria, Clostridium difticile. This bacteha produces toxins
that injure the gut wall, which results in colitis. Patients who take clindamycin, amoxicillin, or cefadroxil should be warned of the possibility of profuse watery diarrhea and told to contact their prescribing dentist if it occurs. The oral cephalosporins are associated with only mild
toxicity problems. As with penicillin, the cephalosporins may cause allergic reactions. They should be given cautiously to patients with penicillin allergies, because these patients may be allergic to the cephalosporins also.
Patients who have experienced an anaphylactic type of • reaction to penicillin should not be given a cephalosporin because of increased chance for that life-threatening event to occur again. The tetracycllnes . have minor toxicities’ for most patients (i.e., the commonly encountered gastrointestinal problems of nausea, abdominal cramping, and diarrhea).

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