Investors might need a little less of AstraZeneca's (NYSE:AZN) heartburn reliever, Nexium, after the drugmaker settled a patent dispute with generic-drug maker Teva Pharmaceuticals (NASDAQ:TEVA) yesterday.

The deal resembles the one AstraZeneca struck with Ranbaxy in 2008, giving Ranbaxy and Teva the right to launch generic versions of Nexium in the U.S. in May 2014, when the first patent on the drug expires. In exchange for not enforcing other patents, AstraZeneca doesn't have to worry about losing a patent challenge in court.

Dr. Reddy's Laboratories (NYSE:RDY), Novartis (NYSE:NVS), and Lupin have also challenged Nexium's patents, but considering the conciliatory moves by Ranbaxy and Teva, it seems likely that the other drugmakers will follow suit.

Nexium is extremely important to AstraZeneca and, to a lesser extent, Merck (NYSE:MRK), which co-markets the drug. The purple pill brought in nearly $3.7 billion -- 15% of AstraZeneca's revenue -- in the first nine months of the year. Sales in the U.S. have been slipping a little because of price cuts, as the drugmaker deals with competition, including generic versions of its own Prilosec, which is available as a over-the-counter version marketed by Procter & Gamble (NYSE:PG).

Unfortunately, investors may have to break out the Nexium again shortly. AstraZeneca has a court case over its patents on cholesterol drug Crestor next month. Crestor is another biggie, coming in third on AstraZeneca's list of top drugs. Crestor's sales are only slightly behind those of Nexium and Seroquel, and it's on pace to catch them shortly, with year-over-year growth of 24% so far this year.

Such is the life of drug company investors. Between FDA decisions and patent disputes, it's difficult to keep your stomach from churning.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Novartis is a Motley Fool Global Gains selection. Procter & Gamble is a Motley Fool Income Investor selection in which the Fool owns shares. The Fool's disclosure policy should make you feel a little better inside.