Congressional Democrats want U.S. Trade Representative Susan C. Schwab to take a tougher line on protecting the intellectual property rights of U.S. drugmakers.

World Trade Organization rules allow developing nations an exception to intellectual property rights in order to make lifesaving medications available, as long as certain rules are satisfied — for example, that the patent holder receives adequate remuneration.

Lawmakers are complaining about Thailand’s use of these exceptions, called compulsory licenses. A group led by Reps. Adam Smith, D-Wash., and Ron Kind, D-Wis., say the Thai government since 2007 has routinely issued compulsory licenses for U.S.-patented medicines, such as several that treat cancer and cardiovascular disease. Smith and Kind say the rules should only be applied to address urgent public health problems such as AIDS, tuberculosis and malaria.

“To help keep American innovation and knowledge-based jobs in the United States, it is essential that the U.S. government continue to stress that such licenses not be issued lightly,” Smith, Kind and 48 other lawmakers wrote Schwab on July 31.

The trade representative’s annual report on intellectual property rights says Thailand’s use of the licenses is inconsistent with the “adequate and effective” protection of those rights.

But House Ways and Means Chairman Charles B. Rangel, D-N.Y., and trade panel Chairman Sander M. Levin, D-Mich., are taking a different approach to the issue, saying a balance must be struck between patent rights and access to medicine for residents of poor countries.

In their June 26 letter to Schwab, also signed by Rahm Emanuel, D-Ill., and Chris Van Hollen, D-Md., the lawmakers wrote: “Improving access to medicines in developing countries is not only a vital humanitarian objective; it also has the potential to expand opportunities for innovative U.S. pharmaceutical companies. Pharmaceutical companies gain nothing when patients in developing countries have inadequate access to their products.”