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 Allergan (NYSE: AGN), a global integrated-health-care company comprised of branded pharmaceuticals and medical devices, jumped as much as 17% after confirming it had received an unsolicited takeover offer from Valeant Pharmaceuticals (NYSE:BHC).

So what: According to Allergan's press release, it has received a takeover offer from Valeant that would pay $48.30 in cash and 0.83 shares of Valeant common stock in exchange for each share of Allergan. Based on the current price of these two stocks as of this writing, this would make Valeant the smaller company purchasing the larger ($44 billion market cap versus $48 billion for Allergan), and place a value of roughly $159 per share on Allergan. As per the press release, Allergan's board is going to carefully review the offer and it advises existing shareholders to take no action at this time.

Now what: I don't say this often, but Allergan shareholders should be thanking their lucky stars that Valeant is willing to pay such a hefty premium for a company that's been mildly disappointing from a growth perspective for the past couple of years. Although its dry-eye treatment Restasis is well-protected by patents, its purchase of MAP Pharmaceuticals to acquire inhaled migraine medication Levadex hasn't worked out, with the company receiving two manufacturing-based CRLs. Even more disappointing, its highly touted experimental vision-loss therapy DARPin failed to excite in midstage studies. This isn't to say other aspects of Allergan aren't growing, but a high single-digit-growth rate for a company valued at nearly 30 times forward earnings doesn't cut the mustard with this value investor. If I were an existing Allergan shareholder I would seriously consider cutting anchor and running with my profit here as the possibility of this offer falling through or being rejected is just too great.