KANSAS CITY, Mo. -- Doctors in Missouri and Kansas may learn this week whether their patients received diluted drugs from pharmacist Robert Courtney.

Meanwhile, federal investigators are looking into whether the dilutions may have dated back as far as 1985, when Courtney first became a pharmacist, FBI spokesman Jeff Lanza said Monday.

Federal authorities announced Friday that Courtney had diluted 72 drugs, dating back to at least 1992 and affecting about 400 doctors and 4,200 patients. He originally admitted to diluting two chemotherapy drugs beginning in November of 2000 and intensifying in March through May of 2001.

Lanza said Courtney now says he diluted the drugs "on virtually every occasion."

"Now, if Courtney is telling the truth ... then doctors getting the letters -- if they received drugs during that time frame -- they were diluted," Lanza said.

The drugs in question were used mainly to treat cancer, but also included antibiotics, iron supplements, blood thinners and drugs to combat the nausea that often accompanies chemotherapy.

Federal investigators say it would be difficult to determine which, if any, drugs were diluted before 1992. Investigators are not sure whether the older records will be retrievable, Lanza said. Pharmaceutical records compiled since 1992 are more accessible because they are kept on computers.

"We aren't sure when this case is going to end, if ever," Lanza said.

A hot line set up to answer calls from people who think they may have received diluted drugs had received 300 calls between Friday and midday Monday, Lanza said.