Investors interested in stocks from the Medical - Drugs sector have probably already heard of Pacira (PCRX) and Zoetis (ZTS). But which of these two companies is the best option for those looking for undervalued stocks? Let's take a closer look.Everyone has their own methods for finding great value opportunities, but our model includes pairing an impressive grade in the Value category of our Style Scores system with a strong Zacks Rank. The Zacks Rank favors stocks with strong earnings estimate revision trends, and our Style Scores highlight companies with specific traits.Currently, Pacira has a Zacks Rank of #2 (Buy), while Zoetis has a Zacks Rank of #3 (Hold). Investors should feel comfortable knowing that PCRX likely has seen a stronger improvement to its earnings outlook than ZTS has recently. However, value investors will care about much more than just this.Value investors analyze a variety of traditional, tried-and-true metrics to help find companies that they believe are undervalued at their current share price levels.The Style Score Value grade factors in a variety of key fundamental metrics, including the popular P/E ratio, P/S ratio, earnings yield, cash flow per share, and a number of other key stats that are commonly used by value investors.PCRX currently has a forward P/E ratio of 25.22, while ZTS has a forward P/E of 38.68. We also note that PCRX has a PEG ratio of 0.76. This metric is used similarly to the famous P/E ratio, but the PEG ratio also takes into account the stock's expected earnings growth rate. ZTS currently has a PEG ratio of 4.58.Another notable valuation metric for PCRX is its P/B ratio of 5.08. The P/B ratio is used to compare a stock's market value with its book value, which is defined as total assets minus total liabilities. For comparison, ZTS has a P/B of 22.48.These are just a few of the metrics contributing to PCRX's Value grade of B and ZTS's Value grade of C.PCRX has seen stronger estimate revision activity and sports more attractive valuation metrics than ZTS, so it seems like value investors will conclude that PCRX is the superior option right now.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Pacira BioSciences, Inc. (PCRX): Free Stock Analysis Report Zoetis Inc. (ZTS): Free Stock Analysis Report To read this article on Zacks.com click here.