What is the appropriate dosing of metronidazole (Flagyl) for pediatric patients?

From the Guidelines

Pediatric patients with infections requiring metronidazole should be dosed at 7.5 mg/kg/dose every 6 hours intravenously, as indicated in the treatment guidelines for mixed infections, including those involving anaerobic bacteria. This dosing recommendation is based on the guidelines provided by the Infectious Diseases Society of America in their 2014 update for the diagnosis and management of skin and soft tissue infections 1. The guidelines outline specific antimicrobial agents and their respective dosages for various types of infections, including mixed infections that may involve anaerobic bacteria, for which metronidazole is often used.

When considering the treatment of pediatric patients, it's crucial to adhere to established guidelines to ensure effective treatment while minimizing the risk of adverse effects. The dosage of 7.5 mg/kg/dose every 6 hours is specified for pediatric patients beyond the neonatal period, highlighting the importance of age-adjusted dosing in pediatric care.

Key points to consider in the administration of metronidazole to pediatric patients include:

• The dose should be adjusted based on the patient's weight to ensure therapeutic levels are achieved without increasing the risk of toxicity.
• Metronidazole can be administered intravenously, which is often the preferred route in severe infections or when oral administration is not feasible.
• Monitoring for potential side effects, such as gastrointestinal upset, is essential, although the guidelines do not provide detailed information on the management of side effects.
• The choice of metronidazole as part of the treatment regimen should be based on the suspected or confirmed causative pathogens and the severity of the infection, as outlined in the guidelines 1.

From the FDA Drug Label

Pediatric Patients 35 to 50 mg/kg/24 hours, divided into three doses, orally for 10 days The recommended pediatric dosing for metronidazole is 35 to 50 mg/kg/24 hours, divided into three doses, orally for 10 days 2.

• The dosage is based on the patient's weight.
• The treatment duration is 10 days.
• The dosing should be individualized for each patient.

From the Research

Pediatric Metronidazole Dosing

• The provided studies do not specifically address pediatric metronidazole dosing, however, some information can be inferred from the pharmacokinetic data.
• According to 3, preterm and term infants have lower total body clearance (CL) and prolonged elimination half-lives of metronidazole, suggesting that dose adjustments may be necessary in this population.
• Children older than 4 years old were observed to have pharmacokinetic parameters similar to those in adults, implying that standard adult dosing may be applicable in this age group 3.
• Reduced CL was also observed in children who are malnourished, which may require dose adjustments 3.
• There is no specific information on the optimal dosing regimen for pediatric patients, and it is recommended to consult current clinical guidelines or a pediatric specialist for guidance on metronidazole dosing in children.

Metronidazole Pharmacokinetics

• Metronidazole has an oral bioavailability approaching 100% and attains concentrations well above the minimum inhibitory concentrations for most susceptible micro-organisms when given intravenously or orally at usual recommended doses 3.
• The drug has limited plasma protein binding but can attain very favorable tissue distribution, including into the central nervous system 3.
• Metronidazole is extensively metabolized by the liver to form 2 primary oxidative metabolites: the hydroxy and acetic acid metabolites, and the kidney is responsible for the elimination of only a small amount of the parent drug 3.

Clinical Use of Metronidazole

• Metronidazole is still the drug of choice for the treatment of anaerobic infections, including those caused by Bacteroides species, fusobacteria, and clostridia 4.
• It is also effective against trichomoniasis, amoebiasis, and giardiasis, and has been used for the treatment of vaginosis due to Gardnerella vaginalis 4.
• Metronidazole-resistant strains have been reported, but combination therapy is still recommended for eradication of certain pathogens, such as Helicobacter pylori 4.