Shares of Express Scripts (ESRX) are plummeting this morning, currently off 13.56%, trading at $54.35. The company issued weak guidance for 2013, noting that Wall Street expectations looked “overly aggressive.”?

With ESRX breaking down through the 200-day moving average, traders are buying upside calls looking for a rebound. Overall call volume us now running at 10.5x normal volume with 48448 contracts traded.

The largest trade has been the purchase of 4,000 February 2013 $60/62.50 call spreads for a net debit of $0.46. 3,339 Feb13 $65 calls were also purchased, on the offer, for $0.24. In May 2013, the $55 call was purchased 1,000 times, on the offer, for $4.05.

In all the above trades, volume exceeded current open interest, indicating new positioning.

30-day implied volatility is off 11.4% today to 28.42%, while 10-day realized vol is registering 23.37%.

Express Scripts Holding Company provides healthcare management and administration services on behalf of its clients, which include health maintenance organizations, health insurers, third-party administrators, employers, union-sponsored benefit plans, workers compensation plans, and government health programs.