R-CHOP is a multi drug regimen that includes rituximab, cyclophosphamide, hydroxydaunorubicin, oncovin and prednisone. Hydroxydaunorubicin is also called as doxorubicin and oncovin as vincristine.
Dacarbazine in vivo converted into methyltriazenoimidazole carboxamide that acts as alkylating agent and produces methylation of O6 of guanine in DNA.
(A) The resistance towards 6-MP is due to alteration of HGPRT
(B) Allopurinol increases the action of 6-MP
(C) Azathioprine is prodrug of 6-MP
(D) 6-MP is given with leucovorin
6-MP can be metabolized by xanthine oxidase enzyme to thiouric acid which is inhibited by allopurinol. Hence allopurinol may increase the levels of methotrexate leading to its toxicity. 6-MP requires bioactivation into 6-thioinosinic acid by the enzyme hypoxanthine-guanine phosphoribosyl transferase
(A) Leucovorin is given along with 5-FU to decrease megaloblastic anemia
(B) Capecitabine is a prodrug of 5-FU converted by tumor specific thymidine phosphorylase
(C) The dose of 5-FU should be reduced in dihydropyridine dehydrogenase deficient patients
(D) Cytarabine inhibits DNA polymerase
Dihydropyridine dehydrogenase is responsible for metabolism of 5-fluorouracil. Patients who are deficient in DPD will have elevated levels of 5-FU in blood leading to its toxicity. Hence the dose of 5-FU should be individualized based on the DPD levels in the patient. Capecitabine is a prodrug of 5-FU. Methotrexate produces megaloblastic anemia and requires leucovorin supplement.