Pfizer's stock rose about 1.5 percent on Tuesday, following a beat on earnings. But some traders are anticipating a tumble for the pharmaceutical giant in the near future.
On Monday, when Pfizer saw more than five times its average daily put volume, one trader with an already bearish bet on Pfizer extended a trade of Aug. 28 35 put options to Sept. 4 33.5 puts. Since buying a put allows a trader to sell a stock at a set price at a given time, these trades are profitable if Pfizer's stock falls below $33 by Sept. 4.
Pfizer reported its quarterly earnings before the bell on Tuesday, beating analyst estimates. By midday the stock gained more than 1.5 percent, trading around $34.84. The stock is up about 12 percent this year.
According to CNBC contributor Mike Khouw, Pfizer tends to move only about 1 percent after reporting earnings. However, the company stock usually extends those moves over the next month.
"This isn't a stock that typically moves a whole lot on earnings," Khouw said Monday on CNBC's "Fast Money." "Even though it doesn't move that much in the day after, over the course of the following month it could move a lot, and this trader is betting it'll go lower."
Pfizer is in the middle of finalizing a deal to buy competitor Hospira for about $15 billion, which the company said led to higher legal and acquisition costs that affected earnings.
Read MorePfizer to buy Hospira to boost biosimilar pipeline
Revenue for the company fell 7 percent from a year ago. The company also said its second-quarter results were hurt by the strengthening dollar.
However, the majority of analysts are actually bullish. According to FactSet, 20 analysts covering Pfizer have an average buy rating and an average price target of $37.79.
