What is the appropriate dosing of Trimethoprim-Sulfamethoxazole (Septra) for a 9-month-old male weighing 9.1 kilograms?

From the Guidelines

For a 9.1 kg male infant at 9 months old, the recommended Septra (trimethoprim-sulfamethoxazole) dosing is based on the trimethoprim component at 8 mg/kg/day divided into two doses, as per the most recent and highest quality study available 1. This means the infant should receive approximately 36-37 mg of trimethoprim per day, or about 18 mg twice daily. Using the pediatric suspension (40 mg trimethoprim/200 mg sulfamethoxazole per 5 mL), this translates to 2.3 mL twice daily. The medication should be given at 12-hour intervals, such as 8 AM and 8 PM, and can be administered with or without food, though giving it with food may reduce gastrointestinal upset. Treatment duration depends on the indication - typically 10-14 days for urinary tract infections, but may vary for other conditions. Monitor for side effects including rash, which may indicate an allergic reaction requiring immediate discontinuation. Ensure adequate hydration during treatment. This dosing is appropriate because trimethoprim-sulfamethoxazole works by inhibiting bacterial folate synthesis at two different points, providing synergistic antimicrobial activity, with dosing adjusted for the child's weight to ensure proper drug concentration while minimizing toxicity risk, as supported by the World Health Organization pocket book of hospital care 1. Some key points to consider when administering Septra to infants include:

• The importance of accurate weight-based dosing to minimize the risk of toxicity and ensure effective treatment
• The need for close monitoring of side effects, particularly rash and other signs of allergic reaction
• The potential for gastrointestinal upset and the benefits of administering the medication with food
• The varying treatment durations depending on the specific indication, such as urinary tract infections or other conditions. It's also worth noting that, according to the study 1, for infants >2 months of age and children, the recommended dose for mild-to-moderate infections is 6–12 mg TMP/kg/day in divided doses every 12 h, and for serious infections, it's 15–20 mg TMP/kg/day in divided doses every 6–8 h. However, the study 1 provides more specific guidance for the dosing of co-trimoxazole (trimethoprim-sulfamethoxazole) in children, which is 4 mg kg−1 trimethoprim plus 20 mg kg−1 sulfamethoxazole BD for 5 days for acute otitis media, and 10 mg kg−1 trimethoprim plus 40 mg kg−1 sulfamethoxazole BD for 5 days for urinary tract infection. Given the more recent and specific guidance provided by the study 1, this dosing regimen is recommended for the 9.1 kg male infant at 9 months old.

From the FDA Drug Label

Children: The recommended dose for children with urinary tract infections or acute otitis media is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days. The following table is a guideline for the attainment of this dosage: Children 2 months of age or older: Weight Dose – every 12 hours lb kg Tablets 22 10 - 44 20 1 66 30 1½ 88 40 2 or 1 DS tablet

For a 9.1 kg male, 9 months old, the dose would be calculated as follows:

• 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours
• For a 9.1 kg child, the dose would be:
  • 40 mg/kg x 9.1 kg = 364 mg sulfamethoxazole per 24 hours
  • 8 mg/kg x 9.1 kg = 72.8 mg trimethoprim per 24 hours
• Given in two divided doses every 12 hours, the dose would be:
  • 182 mg sulfamethoxazole and 36.4 mg trimethoprim per dose, every 12 hours Using the provided table, a child weighing 9.1 kg would likely fall between the 20-30 kg range (though not directly listed), but closest to the 10-20 kg (22 lb) range which recommends 1 tablet every 12 hours. However, exact dosing cannot be determined from the table for a 9.1 kg child. Given the provided information and to err on the side of caution, the dose for a 9.1 kg child would be approximately 1 tablet every 12 hours, but this is an estimation and not a direct calculation from the provided table. 2

From the Research

Septra Dosing Information

There is no direct information available in the provided studies regarding the dosing of Septra (trimethoprim-sulfamethoxazole) for a 9.1 kg, 9-month-old male.

Relevant Studies

• The study 3 discusses the treatment of urinary tract infections, including the use of trimethoprim-sulfamethoxazole, but does not provide dosing information for pediatric patients.
• The study 4 compares the effectiveness of trimethoprim-sulfamethoxazole and amoxicillin-clavulanate in the treatment of acute otitis media, but does not provide dosing information for Septra in pediatric patients.
• The study 5 evaluates the susceptibility of various bacterial isolates to commonly used antibiotics, including trimethoprim-sulfamethoxazole, but does not provide dosing information for pediatric patients.
• The study 6 assesses the stability of amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole in rodent feed and water, but does not provide dosing information for pediatric patients.

Key Points

• The provided studies do not offer specific guidance on the dosing of Septra for a 9.1 kg, 9-month-old male.
• It is essential to consult a pediatrician or a reliable medical resource to determine the appropriate dosage of Septra for this patient.
• The studies 3, 4, 5, 6 provide information on the use of trimethoprim-sulfamethoxazole in various contexts, but do not address the specific question of dosing in pediatric patients.