Midsummer is considered prime beach season, but investors know that, more importantly, it's second-quarter earnings season.

With that in mind, this episode of The Motley Fool's Market Checkup is dedicated to heavy hitters in the pharmaceutical industry. Watch and find out how the second-quarter results of four Big Pharma stocks stack up, and what challenges and opportunities lie ahead for them.

In this video, health-care analysts David Williamson and Max Macaluso drill down on Merck's recent results, detailing everything investors need to know, including whether the company is becoming too reliant on its blockbuster diabetes drug Januvia.