How many antibiotic doses are required for a mild infection (MILOS)?

Antibiotic Dosing for Mild Infections (MILOS)

For mild infections without recent antibiotic use (past 4-6 weeks), treatment duration should be 5-10 days, with clinical reassessment at 48-72 hours to determine if therapy should continue or be modified. 1

Treatment Duration by Infection Type

Skin and Soft Tissue Infections (Mild)

• Duration: 5-10 days for uncomplicated mild skin and soft tissue infections 1, 2
• Treatment should continue for a minimum of 48-72 hours beyond when the patient becomes asymptomatic 3
• For impetigo and other superficial infections, 5-7 days is typically sufficient 1

Respiratory Tract Infections (Mild)

• Duration: 7-10 days for mild acute bacterial rhinosinusitis 1
• Clinical reassessment at 72 hours is critical—lack of improvement should prompt either a switch to alternate antimicrobial therapy or reevaluation of the patient 1
• For mild community-acquired pneumonia, 7-21 days depending on pathogen and clinical response 1

Intra-abdominal Infections

• Duration: 4-7 days for established infection when adequate source control is achieved 1
• Longer durations have not been associated with improved outcomes 1
• For acute stomach/proximal jejunum perforations with source control within 24 hours, only 24 hours of prophylactic therapy is needed 1

Key Dosing Principles for Mild Infections

Time-Dependent Antibiotics (Beta-lactams)

• Multiple daily dosing is essential to optimize time above MIC (T>MIC), which is the parameter that best correlates with clinical efficacy 4
• For amoxicillin in mild disease without risk factors: 1.5 g/day divided doses 1
• For amoxicillin-clavulanate in mild disease: 875/125 mg twice daily 1
• Treatment should be taken at the start of a meal to minimize gastrointestinal intolerance 3

Concentration-Dependent Antibiotics

• Fluoroquinolones and macrolides exhibit concentration-dependent killing with prolonged post-antibiotic effects 4
• These agents can be dosed less frequently (once or twice daily) as AUC:MIC or Cmax:MIC ratios correlate with efficacy 4

Critical Reassessment Points

48-72 Hour Evaluation

• All patients should be reassessed at 48-72 hours to determine clinical response 1, 3
• Failure to improve should prompt:
  • Switch to alternate antimicrobial therapy considering limitations in coverage of initial agent 1
  • Reevaluation for complications or alternative diagnoses 1
  • Consider imaging (CT scan), endoscopy, or culture as needed 1

Minimum Treatment Duration

• At least 48-72 hours beyond symptom resolution or evidence of bacterial eradication 3
• For Streptococcus pyogenes infections, minimum 10 days to prevent acute rheumatic fever 3

Common Pitfalls to Avoid

Inappropriate Duration

• Avoid stopping antibiotics prematurely before 48-72 hours of clinical improvement 3
• Do not extend therapy beyond necessary duration—longer courses for mild infections have not shown benefit and increase resistance risk 1

Recent Antibiotic Use

• Prior antibiotic therapy within 4-6 weeks is a risk factor for resistant organisms 1
• These patients should be treated as having moderate disease with broader spectrum agents, not as mild infections 1

Loading Doses

• The loading dose is the most important dose and is independent of renal function 5
• For time-dependent antibiotics in mild infections, standard dosing without loading is typically appropriate 5

Special Populations

Renal Impairment

• Patients with GFR <30 mL/min require dose adjustment 3
• For GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours depending on severity 3
• For GFR <10 mL/min: 500 mg or 250 mg every 24 hours 3

Pediatric Patients (≥3 months, <40 kg)

• Mild infections: 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours 3
• Severe infections: 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours 3