1. What factors are important in the choice of a suitable antibiotic for dental infection?



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1. What factors are important in the choice of a suitable antibiotic for dental infection?

General guidelines for antibiotic selection include a clinical and microbial diagnosis as well as the patient’s medical and drug history. Knowledge of drug-drug interactions is crucial to prevent unexpected adverse side effects, such as an anaphylaxis reaction to penicillin. Clinicians should select the most effective antibiotic with the least toxic side effects. In selecting a regimen for a pre-existing dental infection, one of the early steps is deciding which antibiotic classification to prescribe. Antibiotics are classified based on mechanism of action, spectrum of activity, and whether bactericidal or bacteriostatic. The more virulent and wide spread dental infections require a more aggressive antibiotic, such as a bactericidal agent. Gram staining and culturing of purulent drainage allow a clinician to make a more accurate selection based on the microbial diagnosis. A review of the patient’s history of present illness and an extensive exam to evaluate duration, swelling, fever, drainage, trismus, dysphagia, dyspnea, or other systemic involvement is crucial. Penicillin VK is still the gold standard in initial treatment of odontogenic infections because of its bactericidal action against both anaerobic and aerobic bacteria, low toxicity, low cost, and relatively narrow spectrum of activity. The bacteria found in odontogenic infections are indigenous, mixed (gram-positive and gram-negative), and in progressed stages predominantly anaerobic. Clindamycin is the first line choice for patients allergic to penicillin.


2. What is the proper duration of antibiotic treatment for dental infections?
The best guide in determining duration of antibiotic treatment is clinical improvement of the patient. Since most odontogenic infections persist for only 2-7 days after removal of the source of the infection, a standard regimen should only extend for 7 days. Patients requiring antibiotic care should be monitored daily and should display improvement in symptoms after 48 hours. Duration of antibiotic treatment is also depending on the individual’s current immune status. Ideally, patients should continue to remain on antibiotic therapy 3-4 days following cessation of symptoms. Extending the duration of treatment further without changing antibiotics is likely to be ineffective because of bacterial resistance.

3. What is the difference between bactericidal and bacteriostatic antibiotics? Which type is preferred for the treatment of dental infections? Can a bacteriostatic agent become bacteriocidal? Which antibiotics used for dental infections are bacteriostatic and which are bactericidal?
Bactericidal agents kill microbes. This is usually accomplished by inhibiting cell wall synthesis. Common bactericidal agents are Penicillins, Cephalosporins, Ciprofloxacin, and Metronidazole. Bacteriostatic is described as inhibiting bacterial growth or multiplication without harming them otherwise. This is usually accomplished by interfering with bacterial protein production or DNA replication. Upon removal of the bacteriostatic agents, microbes usually start to repopulate the area again. Common bacteriostatic agents are Macrolides, Lincosamides, Sulfonamides, and Tetracyclines. Yes, at low doses Clindamycin is bacteriostatic, but at higher doses acts as a bactericidal agent.
4. What is the difference between a narrow-spectrum and a broad-spectrum antibiotic? Which type is preferred for the treatment of a non-life threatening dental infection? Which antibiotics used to treat dental infections are considered to be narrow-spectrum and which are considered to be broad spectrum?
A narrow-spectrum antibiotic is always the preferred treatment for non-life threatening dental infections. A broad-spectrum antibiotic is one that acts against a wide range of bacteria, both Gram-positive and Gram-negative. A narrow-spectrum antibiotic is one that effective against a specific family or class of bacteria (i.e. specific for the pathogen). An advantage of narrow-spectrum antibiotics is less development of drug resistance, less GI disturbance (i.e. C. difficille), and less overall side effects. If the cause of the infection is completely unknown, a broad-spectrum antibiotic or combination therapy is indicated. Classification of drugs of broad vs narrow spectrum is more relative to comparing drugs. For example, some would classify Penicillin VK a broad spectrum, while other as a narrow spectrum.

Narrow Spectrum = Penicillin VK, Penicillin G, Erythromycin

Broad Spectrum = Amoxicillin, Augmentin, Ampicillin, Ciprofloxacin, Cephalexin
5. What are loading and maintenance doses? What are the loading and maintenance doses for antibiotics commonly used to treat dental infections. How are these doses altered for pediatric, pregnant, and elderly patients?
A loading dose is an initial dose higher than the maintenance dose, and is recommended when the half-life of the antibiotic is longer than 3 hours or when there is a delay of 12 hours or more to achieve a therapeutic blood level. Due to the rapid need to treat odontogenic infections, a loading dose is usually advisable to prevent a substantial delay in achieving therapeutic blood levels. A loading dose of 2x the maintenance dose is usually recommended for acute infections.

Pen VK = Loading Dose 2000mg and Maintenance Dose 500mg q6hrs

Clindamycin = Loading Dose 600mg and Maintenance Dose 300mg q6hrs
With all drugs, the FDA classifies them with a pregnancy category [AX] relative to risk. Drugs should only be given during pregnancy when the need has been clearly established. Clindamycin, Amoxicillin, Penicillin, and Vancomycin have been rated at Category B for use in pregnancy. In pregnancy, Amoxicillin is recommended to have shorter dosing intervals and/or increased dosage to attain the same desired plasma concentrations. Clindamycin has no recommended dosage alterations. Consultation with an OB/GYN may be recommended.
As a rule, dosage and/or dosage intervals in pediatrics and elderly patients should be reduced. As with pregnancy, the change in dosage is specific for the individual drugs. With pediatrics, dosage can be calculated by weight. In general, elderly patients have increased fat, decreased total body water, decreased glomerular filtration rate, and decreased hepatic function. Due to these and other reasons, both dosage and/or dosage intervals should be lowered in geriatrics to avoid excessive side effects and overdose.
6. How is oral candidiasis treated?
Oral candidiasis is a topical fungal infection of the oral cavity commonly found in patients with poor oral hygiene with complete dentures, prolonged antibiotic use, and immunosuppressed individually. Topical anti-fungal oral suspensions, tablets, or troches are available for treatment. Nystatin (Mycostatin) is a fungicidal agent commonly used to treat oral candidiasis. An advantage of topical treatment is limited systemic involvement. Topical anti-fungals should be “swished and swallowed” to allow contact with pharyngeal tissues to prevent recolonization of the oral cavity. For denture users, the effected denture should be thoroughly cleaned and soaked in an anti-infective agent.

Rx: Nystatin, Oral Suspension: 100,000 units/mL Disp 480mL



Sig: 5mL swished for 2 minutes and swallow 4 times per day
7. If a patient is taking regular aspirin, should aspirin be stopped before extractions, scaling and root planing or periodontal surgery? Do INR (international normalized ratio) values need to be determined before dental procedures that cause bleeding? Why? What are some adverse effects of aspirin?
Anticoagulation therapy (i.e. Aspirin) should not be stopped or altered prior to extractions, SRP, or periodontal surgery unless recommended by their cardiologist. The risk for a cardiovascular accident or myocardial infarction outweighs the risk of excessive bleeding. INR values are determined to evaluate Coumadin therapy. Aspirin irreversibly inhibits the action of platelets aggregation by inhibiting thromboxane A2; it has no effect on the INR value. INR measures the extrinsic pathway or prothrombin time. A measure of Aspirin is taken with a Bleeding Time, which is prolonged. Adverse side effects of ASA use include GI bleeding, peptic ulcers, tinnitus, excessive bleeding with other anticoagulants, and Reye’s Syndrome.
8. Are there any precautions when prescribing or recommending NSAIDs to a hypertensive patient taking anti-hypertensive medications?
Yes. NSAIDs can increase hypertension by antagonizing the effects of antihypertensives, leading to an increase in arterial blood pressure. For example, Angiotensin converting enzyme inhibitors (ACEIs) in combination with NSAIDS can demonstrate this effect. NSAIDs inhibit prostaglandin-mediated vasodilation, promote salt/water retention, and affect renin, which can partially reverse effects of antihypertensives. Increases in BP is normally limited to <10mmHg. Patients need to be warned of adverse side effects with this combination of drug therapy.
9. Why is there concern about using too much acetominophen? What are Tylenol #1, #2, #3, and #4? What is the usual dose of codeine/acetaminophen?
Excessive acetaminophen (APAP) intake is the leading cause of acute liver failure (i.e. hepatotoxicity). The new recommended maximum daily intake is now 3,000mg for adults. APAP accounts for a significantly high number of overdoses in the US. Many OTC products contain Acetaminophen and can attribute to an accidental overdose. Tylenol #1 is 300mg APAP and 8mg Codeine, Tylenol #2 (300/15mg), and Tylenol #3 (300/30mg). APAP and Codeine combination is available as oral tablets for mild-moderate post-operative pain. 60mg of Codeine is the ceiling dose for this analgesic. Tylenol #1, 2, 3 are classified as Schedule III drugs due to low dependence.
10. What is the best analgesic for mild dental pain (e.g. after scaling and root planing, restorative dentistry)? After moderate dental pain (periodontal surgery, endodontic therapy)? After severe pain (extraction of impacted wisdom teeth, extensive periodontal surgery, and acute pulpitis)?
The “best analgesic” for any pain is relative to the individual patient and depends on their medical history, duration of pain, intensity of pain, and current medications and allergies. Mild dental pain can be managed with OTC 400mg Ibuprofen or 1000mg Acetaminophen. The best analgesic for moderate dental pain is a combination NSAID therapy of Ibuprofen 600mg and Acetaminophen 1000mg. This combined therapy has a synergistic effect that is higher than either single drug. 600mg Ibuprofen achieves an anti-inflammatory level and limits the side effects commonly seen with 800mg. For those unable to take Aspirin-like drugs with moderate pain, Tylenol #3 (300mg APAP/30mg Codeine) works well. For severe pain, a stronger narcotic in combination with NSAID therapy works well. A common Rx for acute pulpitis is Ibuprofen 600mg + Norco (Hydrocodone 10mg / APAP 325mg). Schedule II drugs are rarely required for dental pain.
REFERENCES
Swift JQ, Gulden WS. Antibiotic therapy – managing odontogenic infections. The Dental Clinics of North America. 2002 (46)pp623-633.
American Association of Endodontists (AAE). Use and Abuse of Antibiotics. Colleagues for Excellence. Winter 2012. pp1-8.
Pallasch TJ. Antifungal and antiviral chemotherapy. Periodontology. 2000 (29) pp240-255.
Nahum GG, Uhl K, Kennedy DL. Reviews: Antibiotic Use in Pregnancy and Lactation. Obstetrics & Gynecology. 2006. Vol 107 (5) pp1120-1138.
Little JW, Falace DA, Miller CS, Rhodus NL. Dental Management of the Medically Compromised Patient. 2007. Chapter 10: pp904-927.
Hargreaves KM, Berman LH. Endodontic Pharmacology: A Flexible Analgesic Strategy. Pathways of the Pulp. 2010: 10th edition. Chapter 19. pp 686.


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