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.

What: Shares of Auxilium Pharmaceuticals (NASDAQ: AUXL) have lost roughly 18% of their value today following the company's guidance reduction last night.

So what: Auxilium snuck in several hours after the closing bell on Tuesday to shred its earlier guidance by a fairly substantial amount. Its original full-year revenue guidance had been in a range of $450 million to $490 million, and its original adjusted earnings projection had ranged from $45 million to $50 million, which works out to earnings of $0.91 to $1.01 per share based on the company's current share count. However, its new full-year guidance anticipates revenue in the $380 million to $420 million range, with a new bottom-line guidance range that starts at a $15 million loss and ends at breakeven, working out to a loss per share of $0.30 to breakeven. Analysts had expected Auxilium's full-year revenue to reach $484.1 million and had sought $0.96 in EPS.

Now what: This is an ugly revision, make no mistake. Auxilium blames the shortfall on low revenues from its Testim testosterone gel, which had brought in $45.5 million in the first quarter of 2013 but should only drive $11 million to $13 million in revenue for the same quarter this year. Investors don't want to see excuses, they want to see results, and Auxilium's results are, well, not good. The company might reverse its woes later in the year, but it seems more likely that there's more pain in store. I'd keep my distance for the time being.