What is the treatment for streptococcal (strep) pharyngitis using intramuscular (IM) injection?

From the Guidelines

Penicillin G benzathine injection is the recommended treatment for strep throat (Group A Streptococcal pharyngitis) when an injectable option is needed, with a dose of 600,000 U for individuals weighing less than 27 kg and 1,200,000 U for those weighing 27 kg or more, given as a single intramuscular injection. This recommendation is based on the strongest and most recent evidence from the Infectious Diseases Society of America guidelines 1. The use of penicillin G benzathine injection is particularly useful for patients who cannot take oral antibiotics, have difficulty with medication adherence, or have severe infections.

The benefits of using penicillin G benzathine injection for strep throat include:

• Effective elimination of the streptococcal bacteria that cause the infection
• Prevention of serious complications like rheumatic fever and kidney inflammation
• Rapid decrease in contagiousness
• Reduction in transmission of GAS to family members, classmates, and other close contacts of the patient
• Allowance for the rapid resumption of usual activities
• Minimization of potential adverse effects of inappropriate antimicrobial therapy

It is essential to note that the injection may cause pain at the injection site, and some patients may experience allergic reactions, so it's crucial to report any history of penicillin allergy before receiving the injection. For penicillin-allergic patients, alternative antibiotics like clindamycin or macrolides may be used instead, though these would typically be given orally rather than by injection 1.

Key considerations for the use of penicillin G benzathine injection include:

• Accurate diagnosis of streptococcal pharyngitis to prevent inappropriate administration of antimicrobials to large numbers of patients with nonstreptococcal pharyngitis
• Exclusion of the diagnosis of GAS pharyngitis to prevent unnecessary exposure to the expense and hazards of antimicrobial therapy
• Awareness of the potential for antimicrobial resistance among common pathogens, which can be mitigated by appropriate use of antibiotics 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Streptococcal (Group A) Upper Respiratory Infections (for example, pharyngitis) Adults—a single injection of 1,200,000 units; older pediatric patients—a single injection of 900,000 units; infants and pediatric patients under 60 lbs. —300,000 to 600,000 units. The recommended dosage for strep throat (Streptococcal pharyngitis) is:

• Adults: a single injection of 1,200,000 units
• Older pediatric patients: a single injection of 900,000 units
• Infants and pediatric patients under 60 lbs: 300,000 to 600,000 units 2

From the Research

Strep Throat Injection

• Strep throat, also known as streptococcal pharyngitis, is a common infection that can be treated with antibiotics 3.
• The treatment of choice for strep throat is penicillin, which can be administered orally for 10 days or as a single injection of intramuscular benzathine penicillin 3.
• Amoxicillin is also an effective treatment option and is often preferred due to its better taste and palatability 3.
• Other antibiotic options, such as erythromycin and first-generation cephalosporins, can be used in patients with penicillin allergies 3.

Effectiveness of Antibiotics

• Antibiotics have been shown to provide only modest benefits in treating sore throat, although their effectiveness increases in people with positive throat swabs for group A beta-haemolytic streptococci (GABHS) 4, 5.
• The use of antibiotics can help alleviate symptoms, shorten the duration of illness, and prevent clinical relapse, but the evidence is not conclusive 4, 5.
• There is no clear evidence that one antibiotic is more effective than another in treating GABHS pharyngitis, and the choice of antibiotic should be based on individual patient needs and circumstances 4, 5.

Administration of Antibiotics

• Penicillin can be administered orally or as an injection, and the choice of administration route depends on individual patient needs and circumstances 3.
• A single injection of intramuscular benzathine penicillin can be an effective treatment option for strep throat, especially in patients who have difficulty taking oral medications 3.
• However, the use of injections should be reserved for patients who are unable to take oral medications or who have a history of non-adherence to oral antibiotic regimens 3.

Clinical Decision Rules

• Clinical decision rules, such as the Centor score, can be used to assess the risk of group A beta-hemolytic streptococcal infection and guide antibiotic prescribing decisions 3, 6.
• Rapid antigen testing can be used to confirm the diagnosis of strep throat and guide antibiotic treatment decisions 3, 6.
• Patients with a negative rapid antigen test result may require a throat culture to confirm the diagnosis, especially in children and adolescents 6.