Dosage and Administration
Administration
Administer orally, by slow IV injection or infusion, or by IM injection.
Parenteral route used for treatment of moderately severe or severe infections. Oral route should not be used for initial treatment of severe, life-threatening infections, but may be used as follow-up after parenteral ampicillin.
Oral Administration
Administer orally with a full glass of water 1 hour before or 2 hours after meals.
IV Administration
Reconstitution
Reconstitute vials containing 125, 250, or 500 mg with 5 mL of sterile or bacteriostatic water for injection. Alternatively, reconstitute vials containing 1 or 2 g with 7.4 or 14.8 mL, respectively, of sterile or bacteriostatic water for injection.
Rate of Administration
Solutions reconstituted from 125-, 250-, or 500-mg vials may be given by IV injection over a period of 3–5 minutes. Solutions reconstituted from 1- or 2-g vials should be given IV over a period of ≥10–15 minutes.
For IV infusion, concentration and rate of administration should be adjusted so that the total dose is administered before the drug is inactivated in the IV solution.
IM Administration
Reconstitution
Reconstitute with sterile or bacteriostatic water for injection according to manufacturer's directions to provide solutions containing 125 or 250 mg/mL.
Dosage
Available as ampicillin trihydrate and ampicillin sodium; dosage expressed in terms of ampicillin.
Duration of therapy depends on type and severity of infection and should be determined by clinical and bacteriologic response of the patient. For most infections, therapy should be continued for ≥48–72 hours after patient becomes asymptomatic or evidence of eradication of the infection has been obtained. More prolonged therapy may be necessary for some infections.
Pediatric Patients
General Pediatric Dosage
Oral
Children ≥1 month of age: AAP recommends 50–100 mg/kg daily given in 4 divided doses for mild to moderate infections.
AAP states oral route is inappropriate for severe infections.
IV or IM
Neonates <1 week of age: AAP recommends 25–50 mg/kg every 12 hours in those weighing ≤2 kg or 25–50 mg/kg every 8 hours in those weighing >2 kg.
Neonates 1–4 weeks of age: AAP recommends 25–50 mg/kg every 12 hours for those weighing <1.2 kg, 25–50 mg/kg every 8 hours for those weighing 1.2–2 kg, or 25–50 mg/kg every 6 hours for those weighing >2 kg.
Children ≥1 month of age: AAP recommends 100–150 mg/kg daily given in 4 divided doses for mild to moderate infections or 200–400 mg/kg daily given in 4 divided doses for severe infections.
Endocarditis
Treatment of Endocarditis Caused by Viridans Streptococci or S. bovis
IV
300 mg/kg daily given in 4–6 divided doses for 4 weeks. Used in conjunction with IM or IV gentamicin (3 mg daily given during the first 2 weeks).
Treatment of Enterococcal Endocarditis
IV
300 mg/kg daily given in 4–6 divided doses for 4–6 weeks. Used in conjunction with IM or IV gentamicin (3 mg daily given for 4–6 weeks).
Prevention of Bacterial Endocarditis in Patients Undergoing Certain Dental, Oral, Respiratory Tract, or Esophageal Procedures
IV or IM
50 mg/kg given 30 minutes prior to the procedure.†
Prevention of Enterococcal Endocarditis in Patients Undergoing Certain Genitourinary or GI (except Esophageal) Procedures
IV or IM
For moderate-risk patients, 50 mg/kg given 30 minutes prior to the procedure.†
For high-risk patients, 50 mg/kg (up to 2 g) as a single dose in conjunction with a single dose of gentamicin (1.5 mg/kg) given 30 minutes prior to the procedure followed a dose of IM or IV ampicillin (25 mg/kg) given 6 hours later or, alternatively, oral amoxicillin (25 mg/kg) given 6 hours later.†
GI Infections
Oral
Children weighing ≤20 kg: 100 mg/kg daily in 4 divided doses.
Children weighing >20 kg: 500 mg 4 times daily. Severe or chronic infections may require higher dosage.
IV or IM
Children weighing <40 kg: 50 mg/kg daily in divided doses every 6–8 hours.
Children weighing ≥40 kg: 500 mg every 6 hours. Severe or chronic infections may require higher dosage.
Meningitis and Other CNS Infections
Empiric Treatment of Meningitis
IV
Neonates and children <2 months of age: 100–300 mg/kg daily given in divided doses; used in conjunction with IM gentamicin pending results of in vitro susceptibility tests.
Children 2 months to 12 years of age: 200–400 mg/kg daily given in divided doses every 4–6 hours; used in conjunction with IV chloramphenicol.
Treatment of Meningitis Caused by S. agalactiae
IV
AAP recommends 200–300 mg/kg daily given in 3 divided for neonates ≤7 days of age or 300 mg/kg daily given in 4–6 divided doses for neonates >7 days of age.
Respiratory Tract Infections
Oral
Children weighing ≤20 kg: 50 mg/kg daily in 3 or 4 divided doses.
Children weighing >20 kg: 250 mg 4 times daily.
IV or IM
Children weighing <40 kg: 25–50 mg/kg daily in divided doses every 6–8 hours.
Children weighing ≥40 kg: 250–500 mg every 6 hours.
Septicemia
IV or IM
150–200 mg/kg daily.
Skin and Skin Structure Infections
IV or IM
Children weighing <40 kg: 25–50 mg/kg daily in divided doses every 6–8 hours.
Children weighing ≥40 kg: 250–500 mg every 6 hours.
Urinary Tract Infections (UTIs)
Oral
Children weighing ≤20 kg: 100 mg/kg daily in 4 divided doses.
Children weighing >20 kg: 500 mg 4 times daily. Severe or chronic infections may require higher dosage.
IV or IM
Children weighing <40 kg: 50 mg/kg daily in divided doses every 6–8 hours.
Children weighing ≥40 kg: 500 mg every 6 hours. Severe or chronic infections may require higher dosage.
Adults
Endocarditis
Treatment of Enterococcal Endocarditis
IV
12 g daily (by continuous IV infusion or in 6 equally divided IV doses) in conjunction with IM or IV gentamicin (1 mg/kg every 8 hours). Treatment with both drugs generally should be continued for 4–6 weeks, but patients who had symptoms of infection for >3 months before treatment was initiated and patients with prosthetic heart valves require ≥6 weeks of therapy with both drugs.
Treatment of Endocarditis Caused by HACEK group (i.e., H. parainfluenzae, H. aphrophilus, A. actinomycetemcomitans, C. hominis, E. corrodens, K. kingae)
IV
12 g daily (by continuous IV infusion or in 6 equally divided IV doses) in conjunction with IM or IV gentamicin (1 mg/kg every 8 hours). Treatment with both drugs generally should be continued for 4 weeks.†
Prevention of Bacterial Endocarditis in Patients Undergoing Certain Dental, Oral, Respiratory Tract, or Esophageal Procedures
IV or IM
2 g as a single dose given 30 minutes prior to the procedure.†
Prevention of Enterococcal Endocarditis in Patients Undergoing Certain GU or GI (except Esophageal) Procedures
IV or IM
For moderate-risk patients, 2 g given 30 minutes prior to the procedure.†
For high-risk patients, 2 g as a single dose in conjunction with a single dose of gentamicin (1.5 mg/kg) given 30 minutes prior to the procedure followed by a dose of IM or IV ampicillin (1 g) given 6 hours later or, alternatively, a dose of oral amoxicillin (1 g) given 6 hours later.†
GI Infections
Oral
500 mg 4 times daily.
IV or IM
Adults weighing <40 kg: 50 mg/kg daily in divided doses every 6–8 hours.
Adults weighing ≥40 kg: 500 mg every 6 hours.
Meningitis and Other CNS Infections
IV, then IM
150–200 mg/kg daily in divided doses every 3–4 hours. Use IV initially, may switch to IM after 3 days.
Respiratory Tract Infections
Oral
250 mg 4 times daily.
IV or IM
Adults weighing <40 kg: 25–50 mg/kg daily in divided doses every 6–8 hours.
Adults weighing ≥40 kg: 250–500 mg every 6 hours.
Septicemia
IV or IM
150–200 mg/kg daily.
Skin and Skin Structure Infections
IV or IM
Adults weighing <40 kg: 25–50 mg/kg daily in divided doses every 6–8 hours.
Adults weighing ≥40 kg: 250–500 mg every 6 hours.
Urinary Tract Infections (UTIs)
Oral
500 mg 4 times daily.
IV or IM
Adults weighing <40 kg: 50 mg/kg daily in divided doses every 6–8 hours.
Adults weighing ≥40 kg: 500 mg every 6 hours.
Gonorrhea and Associated Infections
Uncomplicated Gonorrhea
Oral
3.5 g as a single dose (with 1 g of oral probenecid). No longer recommended for gonorrhea by CDC or other experts.
Gonococcal Urethritis
IV or IM
500 mg initially followed by 500 mg 8–12 hours later. No longer recommended by CDC or other experts.
Prevention of Perinatal Group B Streptococcal (GBS) Disease
IV
An initial 2-g dose (at time of labor or rupture of membranes) followed by 1 g every 4 hours until delivery.†
Prescribing Limits
Pediatric Patients
Pediatric dosage should not exceed adult dosage.
Special Populations
Dosage in Renal Impairment
Dosage adjustments necessary in patients with renal impairment.
Some clinicians suggest that adults with GFR 10–50 mL/minute receive the usual dose every 6–12 hours and that adults with GFR <10 mL/minute receive the usual dose every 12–16 hours. Alternatively, some clinicians suggest that modification of usual dosage is unnecessary in adults with Clcr ≥ 30 mL/minute, but that adults with Clcr ≤10 mL/minute should receive the usual dose every 8 hours.
Patients undergoing hemodialysis should receive a supplemental dose after each dialysis period.
Geriatric Patients
No dosage adjustments except those related to renal impairment. (See Renal Impairment under Dosage and Administration.)
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