Penetration into Particular Tissues : Ceftriaxone penetrates the inflamed meninges of neonates, infants and children. ceftriaxone concentrations exceeds 1.4 mg/L in the cerebrospinal fluid (CSF) 24 hrs after IV injection of Rocephin in doses of 50-100 mg/kg (neonates and infants, respectively). Peak concentration in CSF is reached about 4 hrs after IV injection and gives an average value of 18 mg/L. Mean CSF levels are 17% of plasma concentrations in patients with bacterial meningitis and 4% in patients with aseptic meningitis.