What is the recommended dosing of ampicillin (Ampicillin) for the treatment of meningitis?

From the Guidelines

Ampicillin should be administered at a dose of 50 mg/kg every 4 hours (200 mg/kg/day) for the treatment of meningitis, as recommended by the most recent and highest quality study 1. The dosing of ampicillin for meningitis treatment is crucial to ensure effective treatment and prevent complications.

• The recommended dose for children is 50 mg/kg every 4 hours (200 mg/kg/day), with a maximum dose not specified in the study 1.
• For adults, the dose is not explicitly stated in the study, but based on the provided evidence, it can be inferred that the dose should be similar to that of children, around 200 mg/kg/day, divided into doses given every 4 hours.
• The treatment duration for meningitis is generally 7-10 days, but it may be extended to 3 weeks for certain cases, such as infant sepsis and meningitis 1.
• It is essential to note that ampicillin is often used in combination with other antibiotics, such as gentamicin or ceftriaxone, to ensure coverage against common meningitis pathogens, including Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, and Listeria 1.
• Renal function should be monitored during treatment, and dosage adjustments may be necessary for patients with kidney impairment, although this is not explicitly stated in the study 1.
• Another study 1 recommends a dose of 150 mg/kg (8 hours) for ampicillin in patients with bacterial meningitis, but this study is older and of lower quality compared to the study by 1.
• Therefore, the recommendation based on the most recent and highest quality study is to use a dose of 50 mg/kg every 4 hours (200 mg/kg/day) for the treatment of meningitis 1.

From the FDA Drug Label

Bacterial Meningitis Adults and children - 150 to 200 mg/kg/day in equally divided doses every 3 to 4 hours (Treatment may be initiated with intravenous drip therapy and continued with intramuscular injections.) Neonates (less than or equal to 28 days of postnatal age) - Dosage should be based on Gestational age and Postnatal age according to Table 3 Table 3: Dosage in Neonates (less than or equal to 28 days of postnatal age) for Bacterial Meningitis and Septicemia: Gestational age (weeks) Postnatal age (days) Dosage less than or equal to 34 less than or equal to 7 100 mg/kg/day in equally divided doses every 12 hours less than or equal to 34 greater than or equal to 8 and less than 28 150 mg/kg/day in equally divided doses every 12 hours greater than 34 less than or equal to 28 150 mg/kg/day in equally divided doses every 8 hours

The recommended dosing of ampicillin for the treatment of meningitis is:

• 150 to 200 mg/kg/day in equally divided doses every 3 to 4 hours for adults and children.
• For neonates (less than or equal to 28 days of postnatal age), the dosage should be based on Gestational age and Postnatal age according to Table 3, with dosages ranging from 100 mg/kg/day to 150 mg/kg/day in equally divided doses every 8 to 12 hours 2.

From the Research

Meningitis Dosing of Ampicillin

• The recommended dosing of ampicillin for the treatment of meningitis is not explicitly stated in the provided studies as a standalone treatment, but it is often used in combination with other antibiotics.
• A study from 1979 3 compared high- and low-dosage regimens of ampicillin in the treatment of bacterial meningitis, including cases due to Haemophilus influenzae type b, and found that high-dosage regimens offered no benefit over low-dosage regimens.
• Another study from 1975 4 used ampicillin sodium at a dose of 200 mg/kg/day for ten days in children with Haemophilus meningitis, with 31 patients receiving the drug intravenously for ten days and the other 31 patients receiving ampicillin intravenously for five days followed by intramuscular administration for the last five days.
• In cases where ampicillin is used, the dosage and administration route may vary depending on the specific circumstances, such as the age of the patient and the suspected or confirmed causative agent of the meningitis.
• For example, a study from 1991 5 recommends using ampicillin plus cefotaxime in infants up to three months of age, while in adults, ceftriaxone is effective therapy for presumed bacterial meningitis but must be combined with ampicillin initially, since L. monocytogenes meningitis cannot be excluded in most cases until CSF culture results are available.
• The choice of antibiotic and dosage regimen should be guided by the results of cerebrospinal fluid cultures and susceptibility testing, as well as the clinical presentation and response to treatment of the individual patient 6, 7.