If you mean Oframax Forte 1.5 g injection (ceftriaxone 1 g + sulbactam 500 mg), it is a prescription injectable antibiotic. Do not calculate or give it at home.

For a 13-year-old weighing 39 kg, dosing depends on the infection, severity, kidney/liver function, allergy history, and whether it is IV or IM. At this weight, a clinician may use a weight-based pediatric dose or sometimes an adult-type regimen, but the exact frequency and course must be prescribed.

Do not use “1.5 g” as an automatic dose just from age/weight. Confirm the written prescription with the treating pediatrician or pharmacist before administration.

Seek urgent care for breathing difficulty, facial swelling, widespread rash, severe/watery diarrhea, or marked yellowing of eyes/skin after the injection.