Some FDA actions are more meaningful than others. DURECT's (NASDAQ:DRRX) announcement on Monday that the Food and Drug Administration had granted one of its pipeline candidates an orphan drug designation falls into the not-so-meaningful category, although that doesn't make the drug any less interesting.

The compound that received orphan drug status is its potential pain patch Eladur. It is in phase 2 testing as a treatment for post-herpetic neuralgia (PHN), which is essentially shingles-related nerve pain.

Orphan drug designation exists to help make it slightly cheaper and sometimes marginally easier to get a new drug past the FDA and to the market. The biggest benefit, though, is that newly approved orphan drugs get a guaranteed seven years in the U.S. and 10 years in the European Union without generic competition, even if their patents have long ago run out. To be clear, orphan drug designation is not hard to get, and any compound in development to treat a relatively rare disease can get the designation in the U.S.

A quick search of shows many different drugmakers attacking PHN from different angles (but mostly with oral pills). The most comparable PHN compound to DURECT's Eladur pain patch is Endo Pharmaceuticals' (NYSE:ENDP) Lidoderm, which contains a dose of the commonly used local anesthetic lidocaine in patch form (as opposed to DURECT's use of the local anesthetic bupivacaine in its patch).

Sales of Lidoderm were $706 million last year, with prescriptions and sales expected to grow very strongly this year. Large portions of Lidoderm's sales are in indications outside of PHN, though. DURECT is surely hoping to capture some of Lidoderm's on- and off-label revenue if it can successfully commercialize Eladur.

Developing transdermal patch versions of medications approved in other formulations can be a relatively low-risk way to get a compound to the market. Other drugmakers, like Noven Pharmaceuticals (NASDAQ:NOVN), Novartis (NYSE:NVS), and even Johnson & Johnson (NYSE:JNJ), have valuable drugs approved in patch formulations.

Alpharma (NYSE:ALO) is the latest drugmaker to go this route after it paid a relatively cheap $100 million up front and some stock warrants last year to acquire non-steroidal anti-inflammatory drug (NSAID) and pain patch Flector, which the FDA has already approved. Considering that Flector sales are expected to be around $100 million this year, and that peak sales of the drug are expected to reach several hundred million dollars, the value of all pain patches like Eladur has surely gone up as other drugmakers see Flector's and Lidoderm's success.

It could be a few years before DURECT's Eladur reaches the market. With its dirt-cheap valuation and other further-along compounds, like its abuse-deterrent pain drug Remoxy, it won't take a large amount of revenue for DURECT to become a winning investment at these prices if any of its compounds make it to market.