The Senate Monday passed an amendment that would require health officials to certify the safety and effectiveness of prescription drugs imported into the U.S. from other countries.

The measure effectively kills an effort to bring low-cost, drug imports to the U.S.

The Senate's certification amendment, passed on a 49-40 vote, requires health officials to do something they have long said they cannot — monitor drugs manufactured in other countries.

Because of that, the vote undercut a second measure that would permit prescription drug imports from Food and Drug Administration-approved sources in Canada, Australia, Europe, Japan and New Zealand.

Overseas, drugs can cost two-thirds less than they do in the United States, where prices for brand-name drugs are among the highest in the world

Sen. Bernie Sanders, I-Vt., called the certification amendment, introduced by Sen. Thad Cochran, R-Miss., a "poison pill" for the drug-imports legislation. Sen. Byron Dorgan, D-N.D., acknowledged it voided his bid to allow the purchase of drugs abroad.

In many industrialized countries, prices are lower because they are either controlled or partially controlled by government regulation.

Allowing imports from those countries would drive down U.S. brand-name drug prices, Dorgan has said.

The pharmaceutical industry vehemently opposes allowing drug imports, arguing that they could leave the nation vulnerable to dangerous counterfeits.

The Bush administration also opposes allowing imports of prescription drugs, and the White House had threatened a veto.

Both the Cochran and Dorgan measures were amendments to broader FDA legislation.

The idea of allowing prescription drug imports enjoys broad popular support. However, lower prices overseas would not automatically translate into large savings for domestic consumers, according to a 2004 study by the Congressional Budget Office.

The study found that allowing drug imports from a broad set of countries would cut U.S. drug spending by $40 billion over 10 years, about a 1 percent savings.

Similar drug-import legislation is pending in the House.