Antibiotic Overview
The cephalosporins are a group of β-lactam antibiotics that are effective against gram-positive cocci and many gram-negative rods. A large number of cephalosporins are available and are roughly divided into three generations, based on their activity against gram-negative organisms. The first-generation antibiotics have a similar activity, including activity against gram-positive cocci, Escherichia coli, Klebsiella organisms, and Proteus mirabilis.
The second-generation cephalosporins have broader activity against gram-negative bacteria and increased activity against the anaerobic bacteria. The second generation has less activity against the gram-positive cocci than the first generation.
The third-generation cephalosporins are much more active against enteric gram-negative rods but are decidedly less active than first- and second-generation cephalosporins against gram-positive cocci.
Two useful oral cephalosporins are effective in odontogenic infections: (1) cephalexin (Keflex) and (2) cefadroxil (Duricef). Although neither of these is the drug of first choice for odontogenic infections, the drugs may be useful in certain situations in which a bactericidal antibiotic is necessary.
The toxicity of the cephalosporin group is primarily related to allergy. Patients who are allergic to penicillin drugs should be given the cephalosporin antibiotics with caution. Patients who have had anaphylactic reactions to penicillin should not be given the cephalosporins.
The antibacterial spectrum of clindamycin includes the gram-positive cocci and almost all anaerobic bacteria. Clindamycin is effective for streptococci, staphylococci, and anaerobic infections. The drug is more expensive than penicillin and erythromycin and may have increased gastrointestinal toxicity in susceptible patients.
Metronidazole is an antibiotic that is effective only for anaerobic bacteria. Metronidazole has no effect on aerobic bacteria such as streptococci. The drug is primarily used in periodontal disease therapy but may also be useful in the management of anaerobic odontogenic infections alone or in combination with antiaerobic antibiotics such as penicillin.
Penicillin is the drug of choice for odontogenic infections because its antibacterial spectrum includes the gram-positive cocci (except staphylococci) and oral anaerobes. Penicillin G is the form given parenterally, and penicillin V is preferred for oral administration. Penicillin has little toxicity except for allergic reactions, which occur in about 3% of the population.
Penicillinase-resistant penicillins are a group of drugs that are useful for penicillinase-producing staphylococci. Dicloxacillin is the preferred penicillinase-resistant penicillin for oral use. These drugs should be used only for culture-documented infection caused by staphylococci.
Several extended-spectrum penicillins exist. The ampicillin-amoxicillin group is effective against more gram-negative rods than penicillin. Amoxicillin is absorbed better from the GI tract than ampicillin and is thus preferred when the drug is given orally. Amoxicillin is the drug of choice for prevention of bacterial endocarditis because of its excellent GI absorption and slow renal elimination.
The tetracyclines are available for oral and parenteral administration and are generally considered to be broad-spectrum antibiotics. However, common bacterial resistance to these drugs exists. At this time, tetracyclines are useful only against anaerobic bacteria, which forms the basis for their use in odontogenic infections.
The toxicities of tetracyclines are generally low but include staining of developing teeth if given to children or to pregnant or lactating women. Minocycline and doxycycline are preferred because they need to be taken only once or twice daily.
The tetracyclines have an anticollagenase effect. This activity may make them useful for treatment of periodontal and periimplant disease. Doxycycline 100 mg qd may be especially useful.
This family of antibiotics includes ciprofloxacin (Cipro) and ofloxacin (Floxin). The fluoroquinolones are broad-spectrum, bactericidal, orally taken antibiotics. Unfortunately, these drugs are only marginally effective against streptococci and have little or no effect against anaerobic bacteria. Therefore, the usefulness of fluoroquinolones in odontogenic infections is low. The drugs should rarely, if ever, be used empirically for a patient with an odontogenic infection.
The third generation of fluoroquinolones has high antistreptococcal and antianaerobic activity. These drugs may be especially useful when a bactericidal antibiotic is necessary for a patient with severe penicillin allergy. Drugs such as moxifloxacin and levofloxacin are examples of this drug group.
Mucosal candidosis, or oral thrush, should be treated with the topical application of antifungal agents. The two drugs of choice are (1) nystatin and (2) clotrimazole. Both drugs are available as lozenges that are held in the mouth until they dissolve. The patient should use one lozenge 4 to 5 times daily for 10 days for effective control and to prevent relapse of the candidosis.