Shares of drugmaker Shenzhen Hepalink Pharmaceutical Co Ltd soared on the company's trading debut on Thursday against the backdrop of the sharp plunge of the overall market as analysts said it may boost investor interest in the pharmaceutical sector.

The price of Hepalink, the world's largest maker of the blood-thinner heparin, surged 18.36 percent to close at 175.17 yuan ($25.66). It climbed to the intraday high of 188 yuan from its initial public offering (IPO) price of 148 yuan, the highest on record for a Chinese stock.

Analysts said the strong performance of Hepalink indicated investors might turn to pharma shares, seen as a defensive investment in the short term amid the depressed market.

"The surge showed investors are still optimistic about the pharmaceutical sector given its defensive nature and the more favorable government policies to be rolled out soon," said Sun Weina, an analyst at Hongyuan Securities.

Sun noted that, in the short term, the stock does not face the risk of falling below the IPO price, but she warned of the high valuation as it may rekindle IPO fever despite regulators' warnings about overpriced offerings in the domestic stock market.

Hepalink raised 5.9 billion yuan through issuing 40.1 million shares in the most expensive IPO, which was priced at 73 times its 2009 earnings.

The high IPO price made the company's founders, the low-profile couple Li Li and Li Tan, who hold a combined stake of 72 percent, the wealthiest people in China overnight.

Based on the current stock price, the value of the stake exceeded 50 billion yuan ($7.3 billion), surpassing Wang Chuanfu, chairman of electric car manufacturer BYD, China's richest person in 2009 with a fortune of $5.1 billion, according to the 2009 Hurun China Rich List.

US investment bank Goldman Sachs, which paid $4.9 million for 12.5 percent of Hepalink in 2007, also saw a more than 200-fold return based on the current price.

The Shenzhen-based drug company was founded in 1998. It primarily produces herapin, which is purified from pig intestines then made into a shot used to prevent blood clots in patients with heart conditions or undergoing surgery.

As the only Chinese company accredited by the US Food and Drug Administration to export herapin, the company's net profit jumped from 161 million yuan in 2008 to 809 million yuan last year.

It said it would use the funds raised in the IPO to expand production capacity by building a 864 million yuan herapin sodium plant with annual capacity of 5 trillion units.