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Strep Throat. Antibiotics for Streptococcal Pharyngitis.
What is a Strep throat?
Strep throat, also called streptococcal pharyngitis, is an infection with group A beta-hemolytic streptococcus bacteria. Strep throat, has an incubation period of two to five days and is most common in children 5 to 12 years of age. The illness can occur in clusters and is diagnosed most often in the winter and spring. Strep throat causes
Strep throat is caused by Group A beta-hemolytic streptococci which are ordinarily spread by direct person-to-person contact, most likely through droplets of saliva or nasal secretions. Strep throat symptoms
The most common symptoms of strep throat are:
Because many of the signs and symptoms of streptococcal pharyngitis are non-specific it is recommended that the clinical diagnosis is confirmed with laboratory tests. Throat cultures are the conventional gold standard method for confirming the diagnosis. Antibiotics should not be prescribed until the culture result confirms strep throat or another bacterial pathogen. Antibiotic treatment can begin immediately only when:
Antibiotics should be discontinued if the culture result is negative. Antibiotics are commonly used to treat strep throat because they:
Antibiotic selection requires consideration of patient allergies, bacteriologic and clinical efficacy, frequency of administration, duration of therapy, potential side effects, compliance and cost.
Since its introduction in the 1940s, penicillin has been the “gold standard” treatment for strep throat and still remains the drug of choice in many cases of strep throat. The ability of penicillin and other penicillin antibiotics (e.g., amoxicillin) to kill group A streptococci has not changed in more than 50 years. There has never been a group A streptococcus grown from a person that has been resistant to penicillin. Penicillin has proven efficacy and safety and low cost. It is a narrow-spectrum agent that does not promote antimicrobial resistance. Penicillin V dosage:
Amoxicillin, a broader spectrum penicillin, may have some advantages because of higher blood levels, longer plasma half life, and lower protein binding activity. Suspensions of this drug taste better than penicillin V suspensions, and chewable tablets are available. However, gastrointestinal side effects and skin rash may be more common with amoxicillin. Amoxicillin has no microbiologic advantage over the less expensive penicillin. Some studies show that amoxicillin given just once a day may work as well as penicillin V given more often. Amoxicillin dosage:
Amoxicillin/Clavulanate Potassium. The combination drug amoxicillin-clavulanate potassium (Augmentin) is resistant to degradation from beta-lactamase produced by copathogens that may colonize the tonsillopharyngeal area. Amoxicillin-clavulanate is often used to treat recurrent streptococcal pharyngitis. Its major adverse effect is diarrhea. Also it is expensive. Amoxicillin/Clavulanate Potassium dosage:
Alternative antibiotics must be used in patients with penicillin allergy, poor compliance or penicillin treatment failure. Patients who do not respond to initial treatment should be treated with antibiotic that is not inactivated by penicillinase-producing organisms (e.g., amoxicillin-clavulanate potassium, a cephalosporin or a macrolide). Azithromycin is one of the most widely studied antibiotics for the treatment of group A beta-hemolytic streptococcus (GABHS) infections. Azithromycin has the advantage of simpler and shorter dosing regimens compared with penicillin V. Also, new macrolide azithromycin has a similar effectiveness to old erythromycin but may cause less gastrointestinal side effects. Azithromycin can be taken once daily and produces high tonsillar tissue concentrations. A 5-day course of azithromycin is approved by the FDA as a second-line therapy for the treatment of individuals 16 years of age or older with group A streptococcus pharyngitis. The recommended dosage is 500 mg as a single dose on the first day, followed by 250 mg once daily for 4 days 1. For children a total dose of 60 mg/kg azithromycin given during 3 or 5 days (12 mg/kg once daily for 5 days or 20 mg/kg once daily for 3 days) provides an alternative treatment to standard penicillin therapy in cases of penicillin hypersensitivity, when patient is unwilling to a 10-day penicillin regimen or for patients who fail therapy with penicillin antibiotics2. Azithromycin dosage:
Several studies indicate that a 10-day course of a cephalosporin is superior to penicillin in eradicating group A beta-hemolytic streptococci5. Cephalexin
It is thought that narrower-spectrum cephalosporins such as cefadroxil or cephalexin are probably preferable to the broader-spectrum cephalosporins such as cefaclor, cefuroxime, cefixime, and cefpodoxime. Cephalexin dosage:
Cefuroxime axetil
Currently, the recommended course of Cefuroxime for strep throat is 10 days. However, clinical studies6-7 have demonstrated that short-course (4-5 day) treatment with Cefuroxime axetil is more effective than oral penicillin V in eradicating the infection and is comparable to the standard oral penicillin V regimen in preventing post-streptococcal sequelae. Also, studies have demonstrated that short course of Cefuroxime axetil (20 mg/kg/day (max. 500 mg) in two divided doses for 5 days) is effective treatment for children aged 1-17 years with streptococcal tonsillopharyngitis 6. Cephalexin dosage:
Cefdinir
Cefdinir is an extended-spectrum oral cephalosporin with potent antistreptococcal activity. The FDA has approved the use of a 5-day course of Cefdinir for the treatment of streptococcal pharyngitis. 5-day course of Cefdinir is equal to the standard 10-day treatment with Penicillin V3. However, Cefdinir provides a slightly higher eradication rate of group A streptococcus bacteria than Penicillin V. References
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