Antibiotics for Strep Throat (Streptococcal Pharyngitis)
Updated according to 2012 IDSA Updated Guideline for Managing Group A Streptococcal Pharyngitis 9.
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.
While the terms sore throat, tonsillitis, and "strep" are used interchangeably, there are essential differences between these conditions.
Causes & Spread
Strep throat is caused by Group A beta-hemolytic streptococci (Streptococcus pyogenes) which are ordinarily spread by direct person-to-person contact, most likely through droplets of saliva or nasal secretions.
Group C streptococcus (GCS) is a relatively common cause of acute pharyngitis in college students and adults.
Alpha-haemolytic Streptococci are part of the normal flora in the throat (tonsil and pharynx).
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.
New IDSA guidelines recommend confirmatory throat culture before prescribing an antibiotic4. Antibiotic treatment can be started immediately when:
Antibiotics are commonly used to treat strep throat because they:
Antibiotic selection depends on patient allergies, bacteriologic and clinical efficacy, frequency of administration, duration of therapy, potential side effects, compliance and cost.
What is the best antibiotic for Strep Throat?
According to the recent research8, Penicillin is still considered the best choice to treat streptococcal pharyngitis (for those non-allergic to penicillins).
Cephalosporins are superior for relapse and reccurent infections.
Since its introduction in the 1940s, penicillin has been the “gold standard” antibiotic for strep throat and still remains the drug of choice in most cases. Over the past 50 years the ability of penicillin to kill group A streptococci has not changed. There has never been a group A streptococcus grown from a human that has been resistant to penicillin.
Penicillin has proven efficacy and safety. It has a narrow-spectrum and so does not promote antimicrobial resistance.
Penicillin V dosage:
Benzathine penicillin G (intramuscular):
When a patient is unlikely to complete the entire course of oral antibiotic, a single intramuscular dose of penicillin G benzathine (Bicillin L-A) is an option.
Amoxicillin, a broader spectrum penicillin, has the advantage of more convenient treatment regimen. Some studies show that amoxicillin given just once a day may work as well as penicillin V given more often. Amoxicillin suspensions taste better than penicillin V suspensions.
However, Amoxicillin has no microbiologic advantage over the less expensive penicillin. Gastrointestinal side effects and skin rash are more common with amoxicillin.
Amoxicillin/Clavulanate Potassium (Augmentin) is resistant to degradation from beta-lactamase produced by pathogens that may colonize the tonsils and pharynx. 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 (Zithromax), a macrolide antibiotic, is an effective
treatment for group A streptococcal pharyngitis and is considered a second-line therapy.
Azithromycin produces high tonsillar tissue concentrations. Azithromycin has a similar effectiveness to old erythromycin but causes less gastrointestinal side effects. Also, it provides very simple and short dosing regimen.
Azithromycin dosage (5-day course):
Clarithromycin (Biaxin) is reasonable for patients allergic to penicillin. One study suggests that 10 days of clarithromycin may be more effective in eradicating group A streptococci than 5 days of azithromycin 10.
Clindamycin resistance among GAS isolates in the United States is approximately 1%, and this is a reasonable choice for treating penicillin-allergic patients 4.
Several studies indicate that a 10-day course of a cephalosporin is superior to penicillin in eradicating group A beta-hemolytic streptococci5.
Narrower-spectrum cephalosporins such as cefadroxil or cephalexin are preferable to the broader-spectrum cephalosporins such as cefaclor, cefuroxime, cefixime, and cefpodoxime.
Cefadroxil allows a once daily dosing, has a low incidence of gastrointestinal side effects and a good taste.
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 also very effective in eradicating the infection and preventing post-streptococcal sequelae.
Also, 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.
Cefuroxime axetil dosage:
Cefdinir (Omnicef) 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.
Antibiotics NOT recommended for streptococcal pharyngitis:
Published: January 20, 2009