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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:

  • sore throat
  • high temperature, usually over 38°C (101°F)
  • swollen lymph glands in the neck
  • white or yellow spots on the tonsils or back of throat
  • fever and chills
  • headache
  • stomach-ache (especially in children)
Indicators that increase or decrease the likelihood of strep throat
Increased likelihood Decreased likelihood
Age 5-15 years Age 45 years or older
High fever (> 38 °C) Afebrile
Absence of a cough Cough
Exudative pharyngitis or tonsillitis Stuffy, runny nose; conjunctivitis
Anterior cervical adenitis (tender nodes) Hoarseness
Sudden onset of sore throat Diarrhea
Recent close exposure to group A strep Discrete oral ulcerative lesions
Current group A strep epidemic  
Diagnosis

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 for strep throat

New IDSA guidelines recommend confirmatory throat culture before prescribing an antibiotic4. Antibiotic treatment can be started immediately when:

  • Patient is very ill
  • Culture results will be delayed for more than 72 hours
  • Patient follow-up will be difficult

Antibiotics are commonly used to treat strep throat because they:

  • Kill the bacteria and shorten the time the patient is contagious. The patient usually is no longer contagious 24 to 48 hours after starting antibiotics.
  • Prevent rare complications. Although uncommon, strep bacteria can spread to other parts of the body causing ear or sinus infections or an abscess behind or around the tonsils (peritonsillar abscess). Antibiotics may also prevent the infection from triggering immune system to attack itself and cause serious conditions such as rheumatic fever.
  • Relieve discomfort and speed healing to some degree.

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.

Penicillin

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:

  • Children: 250 mg two or three times daily for 10 days
  • Adults: 500 mg two or three times for daily 10 days

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.

  • <27 kg: 600 000 U, 1 dose
  • ≥27 kg: 1 200 000 U, 1 dose
Amoxicillin

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 dosage:

  • Children: 40 mg/kg per day in three divided doses for 10 days
  • Adults: 500 mg three times daily for 10 days

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:

  • Children: 40 mg/kg per day, in two or three divided doses for 10 days
  • Adults: 500 to 875 mg two times daily for 10 days

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

Azithromycin (Zithromax), a macrolide antibiotic, is an effective treatment for group A streptococcal pharyngitis and is considered a second-line therapy.
It is a reasonable choice for patients:

  • allergic to penicillins
  • unwilling to a 10-day regimen
  • who fail therapy with penicillin antibiotics2.

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):

  • Children: The recommended dosage is 12 mg/kg once daily for 5 days. Or, alternatively, 20 mg/kg once daily for 3 days.
    12 mg per kg for 5 days once daily for 5 days
  • Adults: The recommended dosage is 500 mg as a single dose on the first day, followed by 250 mg once daily for 4 days 1.

Clarithromycin

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.

Clarithromycin dosage:

  • Children: 7.5 mg/kg/dose twice daily for 10 days.
  • Adults: 250 mg every 12 hours for 10 days.

Clindamycin

Clindamycin resistance among GAS isolates in the United States is approximately 1%, and this is a reasonable choice for treating penicillin-allergic patients 4.

Clindamycin dosage:

  • Children: 7 mg/kg/dose 3 times daily for 10 days.
  • Adults: 600 mg daily in 2-4 divided doses given for 10 days.

Cephalosporins

Several studies indicate that a 10-day course of a cephalosporin is superior to penicillin in eradicating group A beta-hemolytic streptococci5.

Cephalexin

Narrower-spectrum cephalosporins such as cefadroxil or cephalexin are preferable to the broader-spectrum cephalosporins such as cefaclor, cefuroxime, cefixime, and cefpodoxime.

Cephalexin dosage:

  • Children: 25 to 50 mg/kg per day in two to four divided doses for 10 days
  • Adults: 500 mg two times daily for 10 days

Cefadroxil

Cefadroxil allows a once daily dosing, has a low incidence of gastrointestinal side effects and a good taste.

Cefadroxil dosage:

  • Children: 30 mg/kg once daily for 10 days
  • Adults: 1 g daily as a single dose or in 2 divided doses for 10 days
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 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:

  • Adults and adolescents and (13 years and older): 250 mg two times daily for 10 days
Cefdinir

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.

Unsuitable antibiotics

Antibiotics NOT recommended for streptococcal pharyngitis:

  • Metronidazole - not active against Streptococcus pyogenes
  • Trimethoprim-Sulfamethoxazole (Co-trimoxazole, Bactrim) - does not reliably eradicate pharyngeal infection
  • Tetracyclines - the high prevalence of resistant Streptococcus pyogenes strains.
  • Fluoroquinolones - are expensive and have an unnecessarily broad spectrum of activity.
References
  • 1. Hooton TM. A comparison of azithromycin and penicillin V for the treatment of streptococcal pharyngitis. Am J Med. 1991 Sep 12;91(3A):23S-26S. PubMed
  • 2. Cohen R, Reinert P, De La Rocque F, Levy C, Boucherat M, Robert M, Navel M, Brahimi N, Deforche D, Palestro B, Bingen E. Comparison of two dosages of azithromycin for three days versus penicillin V for ten days in acute group A streptococcal tonsillopharyngitis. Pediatr Infect Dis J. 2002 Apr;21(4):297-303. PubMed
  • 3. Tack KJ, Henry DC, Gooch WM, Brink DN, Keyserling CH. Free in PMC Five-day cefdinir treatment for streptococcal pharyngitis. Cefdinir Pharyngitis Study Group. Antimicrob Agents Chemother. 1998 May;42(5):1073-5. PubMed
  • 4. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America. PDF
  • 5. Casey JR, Pichichero ME. Meta-analysis of cephalosporin versus penicillin treatment of group A streptococcal tonsillopharyngitis in children. Pediatrics. 2004 Apr;113(4):866-82. PubMed
  • 6. Scholz H. Streptococcal-A tonsillopharyngitis: a 5-day course of cefuroxime axetil versus a 10-day course of penicillin V. results depending on the children's age. Chemotherapy. 2004 Apr;50(1):51-4.
  • 7. Adam D, Scholz H, Helmerking M. J Antimicrob Chemother. 2000 Feb;45 Suppl:23-30.
  • 8. van Driel ML, De Sutter AI, Keber N, Habraken H, Christiaens T. Different antibiotic treatments for group A streptococcal pharyngitis. Cochrane Database Syst Rev. 2013 Apr 30;4: PubMed
  • 9. Randel A; Infectious Disease Society of America. IDSA Updates Guideline for Managing Group A Streptococcal Pharyngitis. Am Fam Physician. 2013 Sep 1;88(5):338-340.
  • 10. Kaplan EL, Gooch IW, Notario GF, Craft JC. Macrolide therapy of group A streptococcal pharyngitis: 10 days of clarithromycin is more effective in streptococcal eradication than 5 days azithromycin. Clin Infect Dis 2001;32:1798-802.

Published: January 20, 2009
Last updated: December 07, 2013

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