THE U.S. BAN ON some medicines made by India's largest pharmaceutical company adds a black mark against India's booming drug and drug-testing industries, which already have been under pressure over the country's lax monitoring of drug safety. India's pharmaceutical industry was once the nemesis of U.S. drug companies, producing knock-off versions of patented drugs that grabbed market share. But the two sides have developed a symbiotic relationship in recent years, as India has agreed to enforce international patents and sales of generics have soared worldwide. The U.S. pharmaceutical industry, struggling with patent expirations and too few new products, has cut costs by outsourcing manufacturing and parts of the drug development process to India, China and other low-cost countries. This year, Indian pharmaceutical exports are projected to hit $10 billion up from just $1.9 billion in 1999, according to Global Trade Information Systems, a U.S. supplier of international trade data, and IDFC-SKKI Securities, a Mumbai brokerage firm. But as the industry has grown, so have questions about whether India is ready to play an expanded role in sensitive areas such as early-stage clinical trials