What is the dose of penicillin (Penicillin) for streptococcal (Strep) infections?

From the Guidelines

The recommended dose of penicillin for strep throat is 250 mg taken orally four times daily, or 500 mg twice daily, for 10 days, as supported by the most recent and highest quality study 1.

Key Considerations

• For children, the oral dosage is typically 250 mg two to three times daily for 10 days, with weight-based adjustments for younger children.
• A single intramuscular injection of benzathine penicillin G (1.2 million units) can be given as an alternative.
• The full 10-day course must be completed even if symptoms improve earlier to ensure complete eradication of the bacteria and prevent complications like rheumatic fever.
• Penicillin remains the first-line treatment for strep throat because Streptococcus pyogenes has maintained susceptibility to this antibiotic over decades, and it has a narrow spectrum that minimizes disruption to normal gut flora.

Alternatives for Penicillin Allergy

• For patients with penicillin allergy, alternatives include erythromycin, azithromycin, or first-generation cephalosporins (if no history of anaphylaxis to penicillin) 1.

Management of Symptoms

• Adequate hydration and over-the-counter pain relievers can help manage symptoms while the antibiotic takes effect.

Evidence Base

• The recommendation is based on the 2012 update by the Infectious Diseases Society of America 1, which provides the most recent and highest quality evidence for the treatment of strep throat.
• Other studies, such as those published in 2002 1 and 2009 1, also support the use of penicillin as the first-line treatment for strep throat, but the 2012 update provides the most current and comprehensive guidance.

From the FDA Drug Label

The usual dosage recommendations for adults and children 12 years and over are as follows: Streptococcal infections - mild to moderately severe - of the upper respiratory tract and including scarlet fever and erysipelas: 125 mg to 250 mg (200,000 to 400,000 units) every 6 to 8 hours for 10 days The dose of penicillin for strep is 125 mg to 250 mg (200,000 to 400,000 units) every 6 to 8 hours for 10 days 2.

• The dosage is for mild to moderately severe streptococcal infections of the upper respiratory tract.
• The treatment duration is 10 days.

From the Research

Dose of Penicillin for Strep

• The dose of penicillin for strep is typically 10 days of oral therapy or one injection of intramuscular benzathine penicillin 3
• Penicillin VK, 250 mg three times daily, has been used in clinical trials to treat streptococcal pharyngitis 4
• Amoxicillin is equally effective as penicillin and is often more palatable 3, 5
• The American family physician recommends a 10-day course of penicillin or amoxicillin for the treatment of streptococcal pharyngitis 5

Alternative Treatment Options

• First-generation cephalosporins are recommended for patients with nonanaphylactic allergies to penicillin 3, 5
• Macrolides, such as clarithromycin, have been shown to be effective in treating streptococcal pharyngitis, but resistance has been reported in some areas 4, 6
• Short-course antibiotic treatment (≤5 days) has been compared to long-course antibiotic treatment (≥7 days) in clinical trials, with mixed results 6

Clinical Guidelines

• Clinical guidelines recommend using clinical decision rules to assess the risk of group A beta-hemolytic streptococcal infection, followed by rapid antigen testing if a diagnosis is unclear, before prescribing antibiotics 5
• The modified Centor score can be used to help physicians decide which patients need no testing, throat culture/rapid antigen detection testing, or empiric antibiotic therapy 3