Intracellular deoxyribonucleic acid--modifying activity of intermittent phototherapy.

Phototherapy is capable of damaging the genetic material of eukaryotic and prokaryotic cells at fluences considerably less than that received by irradiated infants. It has been suggested that intermittent phototherapy, with varying on-off cycles, may offer theoretical advantages since the total light dosage received by the exposed infant is reduced. The present study was undertaken to determine the effect of intermittent phototherapy on the genetic material of human cells in tissue culture. Intermittent illumination produced more DNA damage than a similar light dosage administered continuously. These results suggest that intermittent phototherapy regimens may prove more deleterious to irradiated infants than continuous phototherapy.