Ampicillin Dosage

Usual Adult Dose for Bacterial Endocarditis Prophylaxis

Low to moderate risk: 2 g IV or IM 30 minutes before procedure.

High risk: Ampicillin 2 g plus gentamicin 1.5 mg/kg IV or IM 30 minutes before procedure. Follow with ampicillin 1 g IV or IM, or amoxicillin 1 g orally, 6 hours after initial dose.

Usual Adult Dose for Bronchitis

Bacterial exacerbations of chronic bronchitis:
250 to 500 mg orally every 6 hours for 5 to 10 days, depending on the nature and severity of the infection.

Usual Adult Dose for Endocarditis

Enterococcal:
Ampicillin 2 g IV every 4 hours plus gentamicin 1 mg/kg IV every 8 hours for 4 to 6 weeks.

Usual Adult Dose for Gastroenteritis

250 to 500 mg orally every 6 hours.

Usual Adult Dose for Intraabdominal Infection

1 to 2 g IV every 4 to 6 hours in combination with other antibiotics, depending on the nature and severity of the infection.

Duration: 10-14 days.

Usual Adult Dose for Leptospirosis

Moderate to severe: 0.5 to 1 g intravenously every 6 hours.
Mild: 500 to 750 mg orally every 6 hours.

Usual Adult Dose for Meningitis

IV:
200 mg/kg/day (up to 12 g/day) IV in equally divided doses every 4 hours, in combination with other parenteral antibiotics.

Intrathecal or intraventricular:
10 to 50 mg/day in addition to IV antibiotics.

Usual Adult Dose for Peritonitis

CAPD-associated peritonitis: 250 to 500 mg orally twice daily and/or 100 to 125 mg/L exchange intraperitoneally, with or without other antibiotics depending on the nature and severity of the infection.

Secondary: 1 to 2 g IV every 4 to 6 hours in combination with other antibiotics, depending on the nature and severity of the infection.

Duration: 10 to 14 days.

Usual Adult Dose for Pneumonia

Beta-lactamase negative, penicillin-susceptible: 1 to 2 g IV every 4 to 6 hours, in combination with other antibiotic(s) depending on the nature and severity of the infection.

Usual Adult Dose for Prevention of Perinatal Group B Streptococcal Disease

As an alternative to penicillin G: 2 g IV as a loading dose, followed by 1 g every 4 hours until delivery.

Usual Adult Dose for Pyelonephritis

500 mg to 2 g IV or IM every 4 to 6 hours with or without other antibiotics, depending on the nature and severity of the infection.
Duration: 2 to 3 weeks.

Usual Adult Dose for Septicemia

1 to 2 g IV every 3 to 4 hours, in combination with other antibiotics.

Usual Adult Dose for Shigellosis

500 mg orally every 6 hours for 5 days

Usual Adult Dose for Skin or Soft Tissue Infection

250 to 500 mg orally every 6 hours or 1 to 2 g IV every 4 to 6 hours, depending on the nature and severity of the infection.

Usual Adult Dose for Surgical Prophylaxis

Liver transplant: Ampicillin 1 g plus cefotaxime 1 g IV at induction, then every 6 hours for 48 hours after closure.

Usual Adult Dose for Typhoid Fever

Severe, fully susceptible: 25 mg/kg IV or IM every 6 hours for 10 to 14 days.
Carrier state: 1.5 g orally or IV with probenecid 500 mg every 6 hours for 6 weeks.
Fluoroquinolones or amoxicillin are considered the drugs of choice.

Usual Adult Dose for Otitis Media

500 mg orally or 1 to 2 g IV or IM every 6 hours, depending on the nature and severity of the infection.

Usual Adult Dose for Pharyngitis

500 mg orally or 1 to 2 g IV or IM every 6 hours, depending on the nature and severity of the infection.

Usual Adult Dose for Sinusitis

500 mg orally or 1 to 2 g IV or IM every 6 hours, depending on the nature and severity of the infection.

Usual Adult Dose for Upper Respiratory Tract Infection

500 mg orally or 1 to 2 g IV or IM every 6 hours, depending on the nature and severity of the infection.

Usual Adult Dose for Urinary Tract Infection

Mild, uncomplicated: 250 to 500 mg orally every 6 hours
Severe, complicated: 500 mg to 2 g IV every 4 to 6 hours with or without other antibiotics, depending on the nature and severity of the infection.

Usual Pediatric Dose for Bacterial Endocarditis Prophylaxis

Low to moderate risk: 50 mg/kg IV or IM 30 minutes before procedure.

High risk: 50 mg/kg plus gentamicin 1.5 mg/kg, both intramuscularly or IV 30 minutes before procedure. Follow with ampicillin 25 mg/kg IV or IM, or amoxicillin 25 mg/kg orally, 6 hours after initial dose.

Usual Pediatric Dose for Meningitis

Neonates:
< 7 days, birthweight < 2000 g: 50 mg/kg IV every 12 hours.
< 7 days, birthweight > 2000 g: 50 mg/kg IV every 8 hours.
> 7 days, birthweight < 1200 g: 50 mg/kg IV every 12 hours.
> 7 days, birthweight 1200 to 2000 g: 50 mg/kg IV every 8 hours.
> 7 days, birthweight > 2000 g: 50 mg/kg IV every 6 hours.

Infants and children:
50 to 100 mg/kg IV every 6 hours. Maximum dose 12 g/day.

Ampicillin should be given in combination with another antibiotic, depending on the nature of the infection.

Usual Pediatric Dose for Skin or Soft Tissue Infection

IV: 6.25 to 12.5 mg/kg every 6 hours (maximum 12 g/day).

Oral: 6.25 to 12.5 mg/kg every 6 hours (maximum 2 to 3 g/day).

Usual Pediatric Dose for Upper Respiratory Tract Infection

IV: 6.25 to 12.5 mg/kg every 6 hours (maximum 12 g/day).

Oral: 6.25 to 12.5 mg/kg every 6 hours (maximum 2 to 3 g/day).

Usual Pediatric Dose for Surgical Prophylaxis

Liver transplant: Ampicillin 50 mg/kg plus cefotaxime 50 mg/kg at induction and every 6 hours for 48 hours after closure.

Renal Dose Adjustments

CrCl < 10 mL/min: The dosage interval should be increased to every 12 hours.

CrCl 10 to 50 mL/min: The dosage interval should be increased to every 8 to 12 hours.

Liver Dose Adjustments

No adjustment required

Precautions

Oral ampicillin should not be used for initial treatment of severe or life-threatening infections.

Dialysis

Conventional hemodialysis removes 40% of ampicillin. Doses should either be given after dialysis sessions or a supplemental dose should be given on dialysis days.

Other Comments

Absorption is best when oral ampicillin is taken 1 hour before or 2 hours after meals.

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