RIYADH: Nahdi Medical Co., operator of one of the largest pharmacy chains in Saudi Arabia, saw its shares soar almost 21 percent three days into joining the stock exchange. Even though shares edged 0.25 percent lower to SR158 ($42.1) as of Thursday’s close, they rose significantly from the initial public offering price of SR131. With the latest gain, the Jeddah-based company now holds a market valuation as high as SR20.5 billion. Ahead of listing, Nahdi had raised $1.36 billion in the biggest Saudi IPO since oil giant Aramco.