When Congress is done patting itself on the back for improving the prospects for drug safety, it needs to undo legislation it adopted in the spring that could prevent some patients from getting their prescriptions in the first place.

On Thursday, Congress handed the Food and Drug Administration sweeping powers to minimize the potential for harm caused by approved drugs, such as Vioxx. The law, which President Bush is expected to sign, would give the FDA the ability to track the safety of drugs after they go on sale and it would force companies to publicize the results of drug trials. In the past, drug companies have been able to keep secret the safety concerns that arise from trials.

This is certainly good news, but a little-noticed rule slipped into an Iraq war-funding bill in May poses harm on a different front.

The rule mandates tamper-resistant paper for nonelectronic prescriptions written for Medicaid patients. Not a bad idea, given the high cost of Medicaid fraud. The rule was adopted as a way to offset a five-year, $150 million expenditure for public hospitals.

But the deadline for the changeover to tamper-resistant prescription pads is Oct. 1. There’s just no way that all doctors and pharmacists can be expected to comply by then. The rule itself isn’t well-known.

“Nobody really knew where this came from,” said Jamila Edwards of the California Primary Care Association in a USA Today article.

Twelve states require the pads for some drugs, especially the kind that can lead to addictions. Only New York state requires them for all prescriptions. The switch for the other 49 states is much too sudden.

The Medicaid director for Washington state, Doug Porter, notes that few of the state’s doctors use tamper-resistant pads and that some poor and elderly people might be denied their medications when the wrong type of paper is presented. Pharmacists fear denial of payments.

We’re sympathetic to the need to raise money for public hospitals and crack down on prescription fraud. But it’s folly to think of this sudden rule as some sort of cash machine.

It’s a classic case of looking at a budget line and not thinking about its impact on people. Plus, the chaos it creates could very well turn out to be worse than the cure.