Tilray shares posted a 10 percent gain on Monday, followed by surges of 29 percent and 38 percent on Tuesday and Wednesday, respectively.

The stock closed 30.3 percent lower and has posted sharp moves all week. It was also the worst-performing stock in the ETFMG Alternative Harvest ETF (MJ), which fell 7 percent.

The stock was driven higher on Wednesday after CEO Brendan Kennedy told CNBC's Jim Cramer that global pharmaceuticals must think about partnering cannabis producers as a "hedge" against the space. However, trading on the stock was halted five times for volatility before Wednesday's close as it failed to hold a more than 90 percent gain. Tuesday's surge came after Tilray announced the Drug Enforcement Administration approved it to import marijuana to the U.S. for medical research.

But on Thursday, the stock lost some steam as it closed 17.6 percent lower. But even with that decline, Tilray was up more than 40 percent for the week heading into Friday's open. After Friday's decline, the stock was up only 13 percent.

This week alone, Tilray's market cap nearly reached $20 billion earlier in the week before falling back to about $11.5 billion.

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