Should a cephalosporin be used to treat post‑streptococcal glomerulonephritis, and if so, what is the appropriate dosing?

Treatment of Post-Streptococcal Glomerulonephritis with Cephalosporins

Cephalosporins are appropriate alternatives to penicillin for treating post-streptococcal glomerulonephritis when penicillin allergy exists or when beta-lactamase producing organisms are suspected, with first-generation cephalosporins (e.g., cephalexin) preferred for uncomplicated cases and third-generation cephalosporins (e.g., ceftriaxone) reserved for severe infections or resistant organisms. 1, 2

Antibiotic Selection Algorithm

First-Line Therapy

• Penicillin remains the gold standard for PSGN treatment, even when active infection has resolved, as the goal is to reduce streptococcal antigenic load rather than treat active infection 1, 2
• Erythromycin is the alternative for patients with penicillin allergy 1

When to Use Cephalosporins

• First-generation cephalosporins (cephalexin) are appropriate for:

  • Non-anaphylactic penicillin allergies 1, 2
  • Suspected beta-lactamase producing organisms 1
  • Less severe streptococcal skin and soft tissue infections that may lead to PSGN 3

• Third-generation cephalosporins (ceftriaxone) should be used for:

  • Severe infections 1, 2
  • Areas with high prevalence of resistant organisms 1, 2
  • Situations requiring broad coverage against streptococci 1

Dosing Recommendations

While specific dosing for PSGN is not explicitly detailed in the guidelines, standard streptococcal infection dosing applies:

• Cephalexin: Standard dosing for streptococcal infections (typically 250-500 mg orally every 6 hours in adults; 25-50 mg/kg/day divided every 6-8 hours in children) 3
• Ceftriaxone: 1-2 g IV/IM every 24 hours in adults; 50-75 mg/kg/day in children for severe infections 3

Critical Management Principles

Antibiotic Therapy Rationale

• Administer antibiotics regardless of whether active infection is still present—the primary goal is reducing antigenic load, not treating active infection 1, 2
• This is a common pitfall: clinicians may withhold antibiotics when throat culture is negative or skin lesions have healed, but treatment is still indicated 1
• During outbreaks, systemic antimicrobials help eliminate nephritogenic strains of Streptococcus pyogenes from the community 1

Supportive Care Takes Priority

The cornerstone of PSGN management is supportive care, not antibiotics alone:

Fluid and Blood Pressure Management:

• Restrict dietary sodium to <2.0 g/day 1, 2
• Use loop diuretics as first-line agents for fluid overload and hypertension 1, 2
• Target blood pressure <130/80 mmHg (or <125/75 mmHg if proteinuria >1 g/day) 2
• Monitor closely for diuretic complications: hyponatremia, hypokalemia, GFR reduction, and volume depletion 1, 2

Additional Supportive Measures:

• Treat metabolic acidosis if serum bicarbonate <22 mmol/L 1, 2
• Provide dialysis for severe acute kidney injury with uremia, refractory fluid overload, or life-threatening hyperkalemia 1

Immunosuppression: Rarely Indicated

• Reserve corticosteroids ONLY for severe crescentic PSGN with rapidly progressive glomerulonephritis 1, 2
• Do NOT use immunosuppression for typical PSGN—the disease is self-limited with excellent prognosis 1
• Evidence for corticosteroids is anecdotal at best 1, 2

Monitoring Parameters

Complement Levels

• C3 complement should normalize within 8-12 weeks in uncomplicated cases 1, 2
• If C3 remains low beyond 12 weeks, perform kidney biopsy to exclude complement C3 glomerulonephritis (C3GN) 1, 2

Ongoing Assessment

• Monitor serum creatinine, eGFR, blood pressure, urinalysis with microscopy, and urine protein-to-creatinine ratio regularly 1
• Assess for complications including pulmonary edema, congestive heart failure, and hypertensive encephalopathy 4

Special Considerations

Alternative Antibiotics

• Amoxicillin/clavulanate (co-amoxiclav) provides excellent coverage against streptococcal organisms and achieves adequate tissue concentrations 1
• This combination is particularly useful when beta-lactamase producing organisms are suspected 1

When Biopsy is Indicated

Kidney biopsy should be performed when:

• Diagnosis remains uncertain or presentation is atypical 1, 2
• C3 remains persistently low beyond 12 weeks 1, 2
• Rapidly progressive glomerulonephritis with crescentic features is suspected 1, 2

Prognosis

• Most children with epidemic PSGN have excellent prognosis 5, 6
• Adults may have more variable outcomes, with some developing persistent proteinuria or chronic kidney disease 7
• Crescent formation on biopsy and renal insufficiency at presentation predict poor outcomes 4