What pathogens can a single 250mg intramuscular (IM) dose of ceftriaxone treat?

Pathogens Treatable with 250 mg Single Dose IM Ceftriaxone

A single 250 mg intramuscular (IM) dose of ceftriaxone effectively treats Neisseria gonorrhoeae infections at urethral, cervical, rectal, and pharyngeal sites, including both penicillinase-producing and non-penicillinase-producing strains. 1

Effectiveness Against Neisseria gonorrhoeae

Ceftriaxone 250 mg IM provides high and sustained bactericidal levels in the blood that are effective for treating:

• Uncomplicated gonococcal infections of the cervix
• Uncomplicated gonococcal infections of the urethra
• Uncomplicated gonococcal infections of the rectum
• Pharyngeal gonorrhea (which is typically more difficult to eradicate than urogenital or rectal infections)

The CDC guidelines specifically recommend ceftriaxone as the cornerstone of therapy for gonorrhea due to its high efficacy against N. gonorrhoeae, with cure rates of 98.9-99.1% for uncomplicated urogenital and anorectal infections 1.

Pharmacokinetic Advantages

Ceftriaxone's effectiveness against these pathogens is due to its favorable pharmacokinetic properties:

• Provides sustained, high bactericidal levels in the blood
• Has a long half-life (5.8-8.7 hours) compared to other cephalosporins 2
• Single 250 mg IM dose maintains therapeutic concentrations longer than oral cephalosporins 1

Antimicrobial Resistance Considerations

While ceftriaxone remains highly effective against N. gonorrhoeae, there are important resistance considerations:

• The percentage of isolates with elevated minimum inhibitory concentrations (MICs) to ceftriaxone increased slightly from 0% in 2006 to 0.4% in 2011 1
• Among men who have sex with men (MSM), the percentage increased from 0.0% in 2006 to 1.0% in 2011 1
• Current guidelines recommend combination therapy (ceftriaxone plus azithromycin or doxycycline) to improve treatment efficacy and potentially delay emergence of resistance 1

Clinical Evidence

Clinical studies have consistently demonstrated the high efficacy of single-dose ceftriaxone for gonorrhea:

• A retrospective analysis showed that 250 mg IM ceftriaxone eradicated N. gonorrhoeae from 99% of patients, including 99% of urethral/cervical infections, 98% of rectal infections, and 100% of pharyngeal infections 3
• Comparative studies have shown that 250 mg IM ceftriaxone has similar or superior efficacy to other treatments for gonorrhea 4

Important Caveats and Limitations

1. Ceftriaxone has no activity against Chlamydia trachomatis, which commonly co-infects with N. gonorrhoeae 5
2. Current CDC guidelines recommend a higher dose (500 mg) of ceftriaxone plus doxycycline or azithromycin for uncomplicated gonorrhea due to increasing resistance concerns 2
3. For patients with severe cephalosporin allergy, alternative regimens must be considered 1
4. Test-of-cure is recommended for patients treated with alternative regimens and in cases of suspected treatment failure 1

While early studies and some FDA labeling mention other pathogens that ceftriaxone is effective against (including various Gram-positive and Gram-negative bacteria), the 250 mg single IM dose is specifically indicated and proven effective primarily for N. gonorrhoeae infections.