WASHINGTON -- Sen. Kit Bond, R-Mo., wants federal regulators to investigate why the government did not catch a Kansas City, Mo., pharmacist who has admitted diluting prescription drugs.

Robert R. Courtney pleaded guilty in February to watering down two chemotherapy drugs, but FBI officials said recently they believe he may have diluted various drug mixtures prescribed for 4,200 patients since at least 1992. In a letter released Monday, Bond requested that the Food and Drug Administration look for gaps in the regulatory structure that failed to detect Courtney's scheme until a drug salesman helped uncover the dilutions.

"It is clear that the regulatory system is not capable of detecting someone hell-bent on making an extra profit at the direct expense of his patients' well-being," Bond wrote Health and Human Services Secretary Tommy Thompson.

"No matter how one views this evidence, it is clear that the current system has failed thousands of patients and hundreds of doctors in Kansas City," Bond said.

The senator noted he asked Thompson last August whether the government should boost its oversight of the practice. Thompson wrote back that the current system "provides the American public with multiple levels of protection against receiving unsafe, ineffective or poor quality medications."

Bond told Thompson: "That answer was sufficient before the full details of the Courtney case came to light. It no longer suffices now."

Spokesmen for the FDA and HHS did not immediately return telephone calls seeking comment.

Under Courtney's plea agreement, he had to tell prosecutors everything he knew about the dilutions. Based on subsequent interviews with Courtney, the FBI now believes he watered down 72 types of medication, including antibiotics, AIDS medicine, and anti-nausea medications.

Missouri and Kansas health officials last week released lists of doctors and clinics that may have been affected by the dilutions

Courtney, 49, is being held at a private jail for federal prisoners in Leavenworth, Kan. Sentencing has not been set. He faces between 17 1/2 and 30 years in prison.