What antibiotic is recommended for the treatment of mastoiditis?

Antibiotic Treatment for Mastoiditis

First-Line Antibiotic Therapy

Intravenous cloxacillin/flucloxacillin at 50 mg/kg QDS (every 6 hours) for 10 days is the recommended first-line antibiotic for mastoiditis, with adults receiving 2g IV every 6 hours. 1

• Ceftriaxone IV at 50-80 mg/kg daily serves as the second-line option, particularly for penicillin-allergic patients 1, 2
• Initiate antibiotics immediately upon diagnosis, before awaiting culture results 1, 2

Rationale for Antibiotic Selection

The choice of cloxacillin/flucloxacillin is based on the predominant causative organisms:

• Streptococcus pneumoniae remains the most common pathogen despite PCV-13 vaccination 1, 3
• Staphylococcus aureus represents a significant proportion (16.32%) of cases and is increasingly problematic 4
• Other important pathogens include Streptococcus pyogenes, Haemophilus influenzae, and Pseudomonas aeruginosa 1, 3

Alternative Antibiotic Regimens

For complicated mastoiditis or when broader coverage is needed:

• Vancomycin plus piperacillin-tazobactam, OR vancomycin plus a carbapenem, OR vancomycin plus ceftriaxone and metronidazole 2
• High-dose amoxicillin-clavulanate (80-90 mg/kg/day of amoxicillin component, maximum 4000 mg/day) can be used, administered as 1333 mg IV every 8 hours or 2000 mg IV every 12 hours 2
• For confirmed Streptococcus pyogenes, add clindamycin to penicillin therapy 2

Critical 48-Hour Reassessment

Reassess all patients after 48 hours of IV antibiotics to determine if surgical intervention is needed. 1, 2

Indications for surgical intervention include:

• No clinical improvement after 48 hours of IV antibiotics 1, 5
• Clinical deterioration at any point 2
• Presence of subperiosteal abscess 1, 5
• Development of complications (sigmoid sinus thrombosis, intracranial extension) 1, 2

Treatment Success Rates by Modality

Understanding these rates helps guide decision-making:

• Antibiotics alone: 10% success rate 1, 2
• Antibiotics plus myringotomy: 68% success rate 1, 2
• Antibiotics plus mastoidectomy: 22% success rate (but reserved for complicated cases) 1, 2

Duration of Therapy

• Continue IV antibiotics for 7-10 days post-surgery if mastoidectomy is performed 5
• Total antibiotic duration for osteomyelitis involvement: 4-6 weeks 5
• Transition to oral antibiotics based on clinical improvement and culture results 2

Important Clinical Caveats

Prior antibiotic treatment does not prevent mastoiditis development—33-81% of patients with mastoiditis had received antibiotics before admission. 1, 2, 5

• Cultures may be negative in 33-53% of cases, so empiric therapy must be robust 1
• Pain management is paramount throughout treatment 1, 2
• Obtain CT temporal bone with IV contrast if no improvement after 48 hours or if complications are suspected 2, 5
• Consider MRI if intracranial complications (brain abscess, subdural empyema, meningitis, venous sinus thrombosis) are suspected 2

Practical Algorithm

1. Immediate: Start IV cloxacillin/flucloxacillin (or ceftriaxone if penicillin-allergic) + pain management 1
2. Consider: Myringotomy for drainage to improve success rates 1, 2
3. 48 hours: Reassess clinically 1, 2
   • If improving: Continue antibiotics
   • If not improving or worsening: Obtain CT scan and proceed to mastoidectomy 2, 5
4. Monitor: Watch for complications (fever persistence, neurological signs, sigmoid sinus thrombosis) 1, 2