There were 2 new drugs released by the FDA about eight years ago to treat radiation sickness, one for kids and one for adults. I am sure these are well stockpiled by now. I certainly hope those working in Japan’s disaster area have access to these if needed.
Radiation sickness can come about from many different radiation sources. The most common “radiation pill” known is potasium iodine, but it isn’t a cure all for radiation poisoning.
If a nuclear incident occurs, officials will have to find out which radioactive substances are present before recommending that people take KI. If radioactive iodine is not present, then taking KI will not protect people. If radioactive iodine is present, then taking KI will help protect a person’s thyroid gland from the radioactive iodine.
Taking KI will not protect people from other radioactive substances that may be present along with the radioactive iodine.
Here is the FDA’s fact sheet on KI: http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM080542.pdf
Some people can die taking KI, so you have to be careful with it. It isn’t some kind of magical shield against all forms of radioactive isotopes. Basically what happens when you take it is your thyroid absorbs the KI and then if radioactive iodine in ingested, the thyroid is “full” and wont absorb the radioactive stuff and the radioactive stuff passes through your body quicker.
Like I said before, I work in the nuclear industry and I haven’t heard of any new drugs, but that doesn’t necessarily mean that there aren’t some new stuff out there.