Chapter 2:


Jay Elkareh, PharmD, PhD


Orofacial infections are considered mixed infections; they may be caused by either aerobic and anaerobic bacteria or a combination of both. Aerobic bacteria, which require oxygen to survive, include species such as: Streptococcus viridans group, Streptococcus milleri group, beta-hemolytic streptococcus, Staphylococcus aureus, and Staphylococcus epidermis. They can be found in plaque, saliva and other locations in the mouth. On the other hand, anaerobic bacteria do not require oxygen to grow and are often isolated in areas like chronic abscess sites. These bacteria include the following species: Actinomyces, Bacteroides, Eikenella, Fusobacterium, Peptostreptococcus, Prevotella, Porphyromonas, and Veillonella.

1 | Common Indications in Dentistry

Usually, antibiotics are not recommended if the infection is localized, when the patient has a strong immune system, and as a routine prophylaxis measure. (For more information on endocarditis prophylaxis and prosthetic joint infection prophylaxis, refer to section 4: Special Care Patients). When needed, antibiotic treatment must be tailored to each individual case. For instance, an abscessed region will require a different plan of treatment than a systemic infection. While penicillin is the drug of choice for treatment of most empirical infections in and around the oral cavity, other options may need to be considered depending on a patient’s response to the regimen. For example, amoxicillin is better absorbed and tolerated by many patients due to a greater bioavailability and less frequent adverse effects like gastrointestinal upset. For patients allergic to penicillin, clindamycin, azithromycin, or metronidazole may serve as an appropriate alternative. On the other hand, in cases where the patient is not allergic to penicillin but is not responding to first line treatment, adding metronidazole to the regimen or substituting amoxicillin with amoxicillin – clavulanic acid may be a good alternative as the spectrum of sensitivity is altered. The clinician is encouraged to culture oral infection followed by antibiotic sensitivity testing, especially for patients who do not respond to the initial course of antibiotic.

2 | Antibiotic Interaction with Oral Contraceptives

In the past, dental practitioners were encouraged to talk to all women of child-bearing age about the possible reduction in efficacy of oral steroid contraceptives during antibiotic therapy. However, new studies have shown no significant drug–drug interaction between hormonal contraceptives and non-rifamycin antibiotics. Simmons et al. in a 2017 systematic review concluded that the evidence from clinical studies outcomes does not support the existence of drug interaction between non-rifamycin antibiotics and hormonal contraceptives (see Suggested Reading List). As a matter of fact, no significant decrease in progestin levels were observed during antibiotic administration. The dentist should advise their patients to use additional protection where the contraceptive pill effectiveness is compromised in instances such as diarrhea or vomiting, caused by either illness or adverse reaction to the antibiotic.

3 | Antibiotic Selection

An antibiotic can come from natural sources, or it can be semi- or totally synthetic. Regardless of the source, antibiotics are classified as either bactericidal or bacteriostatic. Bactericidal drugs directly kill an infecting organism. These include: beta-lactams (penicillins, cephalosporins, carbapenems, monobactams), metronidazole, fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin), vancomycin, and aminoglycosides. Bacteriostatic drugs inhibit the proliferation of bacteria by interfering with an essential metabolic process, resulting in the elimination of bacteria by the host’s immune defense system. The following drugs are bacteriostatic: tetracyclines (doxycycline, minocycline), macrolides (azithromycin, erythromycin, and clarithromycin), sulfa antibiotics, and clindamycin. In general, there is no advantage in selecting a bactericidal rather than a bacteriostatic antibiotic for the treatment of healthy people. However, if the patient is immunocompromised, either by concurrent treatment (such as cancer chemotherapy or drugs associated with a bone-marrow transplant) or by a preexisting disease (such as HIV infection), a bactericidal antibiotic would be indicated. In general, bactericidal antibiotics should not be used concomitantly with bacteriostatic agents since they may decrease the activity of each.

Over time, the susceptibility of oral bacteria to antibiotics has changed. For example, many gram-positive aerobes and gram-negative anaerobes have shown increased resistance to penicillin. Likewise, aerobic and anaerobic bacteria have developed resistance to some clindamycin regimens. Antibiotic stewardship can limit the development of resistant organisms and enhance patient outcomes. Stewardship emphasizes the responsible use of antibiotics through:

Identifying the circumstances when antibiotics are indicated

Choosing the right antibiotic

Prescribing the right dose and the right duration of therapy

A comprehensive evaluation of every patient is necessary. This involves an assessment of the patient’s medical history, then a clinical examination of the infection site, surgical intervention if needed, administration of a suitable antibiotic, and referral to a specialist if necessary.

Antibiotic treatments range from five to seven days on average or three days after the patient’s symptoms have subsided. The tables in this chapter will provide information about the most frequently prescribed antibiotics in the dental office.

Antibiotic selection depends on:

Oral condition-specific determinations such as topical treatment, systemic treatment, or general prophylaxis

Drug-specific determinations such as the current list of medications the patient is taking, potential drug-drug interactions, and possible side effects/contraindications to the drug to be prescribed

Patient-specific determinations such as age of the patient, pregnancy/breastfeeding status, or any condition that leaves patient medically compromised

Antibiotic-specific determinations affecting drug compliance such as length of treatment, frequency of dosage, dosage form, cost of the antibiotic, availability of a generic/brand name option on the formulary

image | Suggested Reading

Ciancio S, ed. ADA/PDR Guide to dental therapeutics. Fifth ed. Chicago: American Dental Association, 2009.

Flynn TR. What are the antibiotics of choice for odontogenic infections, and how long should the treatment course last? Oral Maxillofac Surg Clin North Am 2011;23(4):519-36.

Holmes CJ, Pellecchia R. Antimicrobial therapy in management of odontogenic infections in general dentistry. Dent Clin North Am 2016;60(2):497-507.

Roberts RM, Bartoces M, Thompson SE, Hicks LA. Antibiotic prescribing by general dentists in the United States, 2013. J Am Dent Assoc 2017;148(3):172-78.e1.

Segura-Egea JJ, Gould K, Sen BH, et al. Antibiotics in endodontics: a review. Int Endod J 2016: 20(6):1133-41.

Simmons KB, Haddad LB, Nanda K, Curtis KM, et al Drug interactions between nonrifamycin antibiotics and hormonal contraception: A systematic review. Am J Obstet Gynecol. 2017 Jul 7. pii: S0002-9378(17)308-45.

Drug Monograph

The following tables list some of the antibiotics commonly used in dentistry.

In the monographs below, prophylaxis includes prosthetic joint infection prophylaxis or endocarditis prophylaxis. The most current guidelines are available at

NOTE: The sample prescriptions in this handbook represent a general recommendation. Clinicians are responsible to adjust the prescription dose, frequency and length of treatment based on the procedure performed, the medicine prescribed, and the patient conditions such as age, weight, metabolism, liver and renal function.

Amoxicillin – A Penicillin

Tablet/Capsule: 250 mg, 500 mg, 875 mg · Chewable tablets: 125 mg, 250 mg Liquid: 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, 400 mg/5 mL


Acute oral infection




Take 1 tablet (500 mg) 3 times a day for 5 to 7 days (15-21 tablets)

For prophylaxis, take 4 tablets (4x 500 mg) 1 hour before dental procedure (4 tablets)


Hypersensitivity to penicillin


Hypersensitivity to cephalosporins, carbapenem, imipenem

Superinfection may occur with prolonged use

Previously confirmed C. difficile-assoc. diarrhea

Patient with infectious mononucleosis


This drug ↓ the effect of live vaccines such as BCG, cholera, typhoid

This drug ↑ the concentration of methotrexate

The following medications may ↓ the therapeutic effects of this drug: – Tetracycline such as minocycline, doxycycline, demeclocycline – Gastroesophageal drugs such as esomeprazole, lansoprazole, dexilansoprazole, omeprazole, pantoprazole – GLP-1 receptor agonist antidiabetic medications such as exenatide, and lixisenatide

Aminoglycosides such as amikacin, gentamicin, streptomycin, tobramycin ↑ the concentration, efficacy and bactericidal effects of this drug


Common reactions:

Nausea, vomiting, diarrhea

Urticaria, rash

Black hairy tongue

Oral or vaginal candidiasis

Less common reactions:

Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis

C. difficile-assoc. diarrhea, hepatitis


Pregnancy Category B

Lactation: drug enters breast milk; use with caution

Adjust dose and frequency of drug to twice a day or daily based on severity of renal impairment

No hepatic dose adjustment needed


Peak serum time: 2 hr, 1 hr (suspension)

Protein bound: 17-20%

Bioavailability: 74-92%

Half-life: 0.7-1.4 hr

Excretion: urine (60% unchanged drug)

Combination Drug (Amoxicillin – Clavulanate)*

Tablet: 250 mg/125 mg, 500 mg/125 mg, 875 mg/125 mg Chewable tablets: 200 mg/28.5 mg, 400 mg/57 mg Liquid: (125 mg/31.25 mg)/5 mL, (200 mg/28.5 mg)/5 mL, (250 mg/62.5 mg)/5 mL, (400 mg/57 mg)/5 mL, (600 mg/42.9 mg)/5 mL


Take 1 tablet (500 mg/125 mg) 3 times a day for 5 to 7 days (15-21 tablets)

* Amoxicillin – Clavulanate shares several pharmacological similarities with Amoxicillin, however refer to the drug package insert or the U.S. Food & Drug Administration (, for a complete drug profile for this medication.

Azithromycin – A Macrolide

Tablet: 250 mg, 500 mg Liquid: 100 mg/5 mL, 200 mg/5 mL

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Acute oral infection




Take 2 tablets (500 mg) on day 1, then 1 tablet on days 2 to 5 (6 tablets)

For prophylaxis, take 2 tablets (2x 250 mg) 1 hour before dental procedure (2 tablets)


Azithromycin hypersensitivity

Hepatic impairment or cholestatic jaundice

Co-administration of antipsychotic drug; pimozide

Feb 15, 2020 | Posted by in Dental Materials | Comments Off on Antibiotics
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