Physicians, under pressure from health plans to curb costs, have less time for, and patience with, persistent sales pitches. The government has been cracking down on aggressive, illegal marketing of drugs for unapproved uses. And drug makers, unable to bring enough new products to market to fully offset patent losses, have been forced to tighten belts. As a result, the industry has slashed 33,000 sales jobs in the U.S. from its peak five years ago, when 105,000 representatives flooded the zone.