Preterm newborns are known to be at higher risk for bronchopulmonary dysplasia with extended exposure to high concentrations of oxygen.  Other groups at higher risk for oxygen toxicity are patients on mechanical ventilation with exposure to levels of oxygen greater than 50%, and patients exposed to chemicals that increase risk for oxygen toxicity such the chemotherapeutic agent bleomycin .  Therefore, current guidelines for patients on mechanical ventilation in intensive care recommends keeping oxygen concentration less than 60%.  Likewise, divers who undergo treatment of decompression sickness are at increased risk of oxygen toxicity as treatment entails exposure to long periods of oxygen breathing under hyperbaric conditions, in addition to any oxygen exposure during the dive. 
Bleomycin is a nonribosomal peptide that is a hybrid peptide - polyketide natural product . The peptide / polyketide / peptide backbone of the bleomycin aglycon is assembled by the bleomycin megasynthetase, which is made of both nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) modules. Nonribosomal peptides and polyketides are synthesized from amino acids and short carboxylic acids by NRPSs and PKSs, respectively. These NRPSs and PKSs use similar strategies for the assembly of these two distinct classes of natural products. Both NRPs and type I PKSs are organized into modules. The structural variations of the resulting peptide and polyketide products are determined by the number and order of modules on each NRPS and PKS protein.
mg/m2 PO/IM daily for 4 to 6 weeks or until remission occurs; followed by twice weekly maintenance therapy with a total weekly dose of 30 mg/m2 PO/IM. Children receiving doses of 20 to 30 mg/m2/week ( to 1 mg/kg/week) may have better absorption and fewer GI side effects if methotrexate is administered either IM or subcutaneous. Several different combination chemotherapy regimens have been used for both induction and maintenance therapy in acute lymphoblastic leukemia. The prescriber should be familiar with new advances in antileukemic therapy.