Bactrim Dosing For A UTI In A 6 Year Old Child

Hello and thanks for your question! We are more than happy to answer this for you.

To start off, it is important to know that Bactrim is a combination drug product, containing both sulfamethoxazole and trimethoprim. They work synergistically as antibiotics.

Bactrim Suspension (also known as Septra) is available in a concentration of sulfamethoxazole/trimethoprim 200mg-40mg/5mL (i.e. 200mg sulfamethoxazole and 40mg trimethoprim per 5mL).

Bactrim UTI Dosage For Children 3-17

The recommended dosage to treat a UTI (urinary tract infection) in children and adolescents aged 3 to 17 years is:

• Per the Prescribing Information For Bactrim: 8mg/kg per day (trimethoprim component) given in two divided doses
• Per the American Academy of Pediatrics: 6-12 mg/kg per day (trimethoprim component) given in two divided doses

So, let's find the dosage for the example you give, a 60-pound female that is 6 and 1/2 years old. We'll use 8mg/kg per day:

• 60 pounds converts to 27.21 kilograms (60 pounds/2.205).
• 8mg (times) 27.21 kilograms equals 217.68 mg trimethoprim per day.
• Bactrim suspension is available in a concentration of 200mg-40mg/5mL.
• Converting 217.68mg trimethoprim per day into a volume (based on 200mg-40mg/5mL) equals 27.21 mL per day.
• Since Bactrim is dosed twice daily, this comes out to ~13.6mL two times daily

One teaspoonful is equivalent to 5mL, so I imagine the doctor in this situation would prescribe either exactly 13.6mL twice daily or 3 teaspoonfuls (15mL) twice daily to ease with measuring.

Final Words

Thanks again for your question and please feel free to reach out again if anything else comes up!