UPDATE 1-India's Ranbaxy beats estimates on higher sales, forex gain

* Net profit 7.5 bln rupees vs estimate 2.92 bln rupees

* North America sales rise 60 pct, India up 13 pct

* Foreign exchange gains at 3.93 billion rupees

MUMBAI, Nov 8 (Reuters) - Ranbaxy Laboratories Ltd , India's top drugmaker by sales, beat estimates with a 7.5 billion rupee ($140 million) quarterly net profit on stronger demand for its generic drugs in its key North American market while foreign exchange gains ballooned.

Demand for cheaper generic medicines from Ranbaxy and its local rivals such as Dr. Reddy's Laboratories Ltd, Cipla Ltd and Sun Pharmaceutical Industries Ltd is booming as developed nations battle rising healthcare costs.

Indian drugmakers, which, on average, draw half of their sales from the United States, account for about a third of applications to sell generic drugs in that country.

They, however, face intense competition, as well as an increase in lawsuits from rival drugmakers and a stricter U.S. regulatory environment.

Ranbaxy, controlled by Japan's Daiichi Sankyo Co, said on Thursday sales grew to 26.5 billion rupees in the fiscal third quarter ended September from 20.2 billion rupees a year earlier. The company gained 3.93 billion rupees in forex gains.

Analysts, on average, estimated the net profit at 2.92 billion rupees on net sales of 26.91 billion rupees, according to Thomson Reuters I/B/E/S. Ranbaxy had posted a loss of 4.65 billion in the year-ago quarter.

Last year it launched the first copy-cat version of Lipitor, the world's top-selling drug owned by Pfizer Inc, in the United States and enjoyed exclusive marketing rights with Watson Pharmaceuticals Inc for six months that ended in May 2012.

It also launched generic Actos, a diabetes drug by Takeda Pharmaceutical Co, in August and shares marketing exclusivity with Mylan Inc in the United States.

Sales in North America jumped 60 percent to 9.2 billion rupees during July-September while formulations business in India grew 13 percent to 5.83 billion rupees, it said.

Shares in Ranbaxy, valued about $4.2 billion, were up down 0.6 percent at 547.3 rupees by 0947 GMT. The stock is up nearly 35 percent this year compared with a near 20 percent rise in Mumbai market.