Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Good morning, fellow Foolish investors! Let's take a closer look at four stocks which could loom large in health care headlines this morning -- Roche (RHHBY -0.03%), Merck (MRK 0.36%), Bayer (BAYR.Y -2.23%), and Regeneron (REGN -0.68%).

Roche bans direct comparisons of biosimilars to Herceptin
First and foremost, Roche recently secured an injunction in India, which prevents generic competitors from comparing biosimilar versions of Roche's blockbuster breast cancer drug Herceptin to the original drug. Herceptin, a targeted treatment which treats HER2-positive breast cancer (15% to 20% of all breast cancers), generated revenue of 6.08 billion Swiss Francs ($6.79 billion) in fiscal 2013.

The injunction is aimed squarely at Mylan and Biocon, which launched the world's first biosimilar version of Herceptin last week in India. India was never a huge market for Herceptin -- in 2012, it only reported $21 million in Herceptin sales from India. Roche attempted to boost sales in India by lowering the price to $1,366 per month (compared to $4,500 in the U.S.).

Since Roche's injunction prevents any direct comparisons between biosimilar versions of Herceptin with the original, it could be difficult for doctors and patients to make an informed decision between the two. Biocon called Roche's injunction "extremely shocking, but not unexpected."

Mylan, the third largest generics manufacturer by revenue in the world by 2012 revenue, is expecting India to become a major pillar of top line growth for the company. In addition to the launch of biosimilar Herceptin, the company signed a deal with Gilead Sciences on January 31 to become its exclusive branded medicines business partner in India, which allows Mylan to distribute Gilead's blockbuster antiviral drugs Viread, Truvada, Stribild, and the systemic fungal infection treatment AmBisome within the country.

Merck settles its NuvaRing lawsuits for over $100 million
Meanwhile, Merck just paid over $100 million to settle over 1,700 lawsuits regarding its NuvaRing contraceptive ring, according to a recent Bloomberg report. The ring was implicated in a higher rate of fatal blood clots than most other competing products.

NuvaRing is a hormonal contraceptive which combines the hormones estrogen and progestin in a vaginal ring to prevent pregnancy. The product was launched in the United States in 2001. The FDA first issued a warning regarding the risk of blood clots in 2011.

Merck reported $686 million in NuvaRing sales in fiscal 2013 -- a 10% jump from the previous year. The product only accounts for 1.6% of Merck's top line, and $100 million isn't a huge settlement for a company which generated $44 billion in sales last year -- but the lawsuits could cause substantial PR damage to the company. Many investors still remember the damaging $4.85 billion settlement Merck paid in 2010 to settle lawsuits regarding 3,468 deaths caused by its Vioxx painkiller. Vioxx, which was pulled from the market in 2004, was found to double the risk of heart attacks and strokes.

Bayer's Aleve gets reevaluated by an FDA advisory committee
Speaking of heart issues, an FDA advisory committee will be reevaluating the safety of Bayer's Aleve (naproxen) this week. The committee will determine if Aleve poses any heart danger at all in patients.

If the review is favorable, Aleve will no longer be required to carry a "heart warning" that is currently standard for all NSAIDs (non-steroidal anti-inflammatory drugs) -- which could result in "a cleaner label and major marketing advantages for Aleve," according to a recent report in The Wall Street Journal.

Aleve competes against other NSAIDs such as Pfizer's Celebrex and Advil, and Johnson & Johnson's Motrin. A recent warning by the FDA stating that acetaminophen painkillers (llike Johnson & Johnson's Tylenol and GlaxoSmithKline's Panadol) could cause liver damage could also boost Aleve sales.

Last quarter, sales of Aleve fell 6% year-over-year to €79 million ($108 million), mainly due to unfavorable currency impacts. The drug accounted for less than 1% of Bayer's overall sales, so an FDA opinion probably won't dramatically affect Bayer's business much either way. However, a favorable ruling for Aleve bodes well for NSAIDs in general, which means that companies which rely on acetaminophen painkillers, such as J&J and GSK, stand to lose market share in consumer health.

Regeneron edges closer to a DME approval for Eylea
Last but not least, Regeneron and Bayer just reported that two-year results from their phase 3 VISTA trial of Eylea for the treatment of DME (diabetic macular edema) showed sustained improvement in patients' vision. The trial notably does not compare Eylea to its main competitor, Novartis' (NYSE: NVS) Lucentis (which is approved for DME), but compares two different doses of Eylea to laser photocoagulation treatment.

Regeneron is relying on an eventual approval of Eylea for DME to improve the drug's already impressive sales. Eylea is currently approved for Wet AMD (age-related macular degeneration) and macular edema following CRVO (central retinal vein occlusion).

Regeneron expects to finish fiscal 2013 with $1.4 billion in Eylea sales, but current peak sales estimates of $4 billion suggest that the drug, which accounted for 61% of the company's top line in third quarter 2013, still has plenty of room to run. Regeneron is expected to release its fourth quarter and full year earnings tomorrow morning.