Shares in online pharmacy PlanetRX.com Inc were well received on the Nasdaq Thursday, opening at $31.50 and jumping as much as 128%, after the company sold six million shares at $16 each. The stock traded up to $36.50 in its maiden session before closing at $26, for a 62.5% premium over the offering price. Volume for the day was 10.9 million shares. Underwriters for the offering were Goldman, Sachs & Co, BancBoston Robert Stephens, Hambrecht & Quist and William Blair & Co. The underwriters will have a 30-day option to purchase up to 900,000 additional shares to cover over- allotments. รก