A patient with cancer received extreme degree of radiation toxicity. Fuher history revealed that the dose adjustment of a paicular drug was missed during the course of radiotherapy. Which of the following drugs required a dose adjustment in that patient during radiotherapy in order to prevent radiation toxicity -: (A) Vincristine, (B) Dactinomycin, (C) Cyclophosphamide, (D) 6-Mercaptopurine
Answer is B. Ans. is 'b' i.e., Dactinomycin o The patient was most probably taking a radiosensitiser i.e., drugs which increases the toxicity due to radiotherpy. o The dose of these drugs should be decreased during radiotherapy o Among the drugs given in the question Actinomycin D or Dactinomycin is a radiosensitizer o Hypoxic cells are resistant to radiotherapy o Augmentation of oxygen is the basis of radiosensitization