Radiosensitization of Staphylococcus aureus by secobarbital sodium and other barbiturates.

The barbiturate hypnotic, secobarbital sodium, at millimolar concentrations, sensitizes Staphylococcus aureus in anoxic buffer-saline suspension (pH 7.0) to the lethal effects of gamma rays. The maximal response represents 50% of that for oxygenated suspensions without additive. Secobarbital sodium operates within the oxygen effect. It must be present at the time of irradiation for modification of radiation response. This, coupled with its testing in the presence of other additives, points to its involvement in an intracellular reaction with a radiation-induced short-lived chemical species, probably the electron. Preliminary tests show that pentobarbital sodium also operates as an efficient hypoxic radiosensitizer. Lack of sensitization by phenobarbital sodium is attributed to its low lipid solubility.