Profit margins for multinational pharmaceutical companies in China are being met with big pains on expiring patents and policy changes.President of the Pharmaceutical Association Committee Zhuo Yongqing said foreign and domestic pharma companies are experiencing slower growth.And while international companies once saw surging profits in years past, a slew of challenges have resulted in a turning of the tides.Drug giants Bristol-Myers Squibb and GlaxoSmithKline have each laid off some 1,000 employees in the past few years, attributing the moves to changes in their business model.Meanwhile, dismissed employees have said the layoffs were due to profit declines.In February, Merck ended a joint venture with its Chinese partner, cutting some 300 jobs in China.Big Pharma has made large investments in China since 2010 to tap booming demand.But according to PharmAsia News, GSK reported a 3 percent decline in sales in China in the first quarter of this year.Eli Lilly and Co. reported 6 percent growth for first-quarter sales of this year, down 21 percent in 2014.Around the world, drug makers are also coming up against a clock running out on patents for some of their best-selling drugs.Foreign drug makers in China have also long contended with lengthy approval processes to enter the market.For new drugs to enter the market, a senior executive at a drug company said it takes five to eight years for registration and then another two years for the drug to appear in state drug procurement catalogs.For Caixin Online, this is Diana Bates.