Shares of Canadian marijuana producer Tilray gave up a 90 percent one-day surge and turned negative briefly in a wild day of trading on Wednesday.
The stock, which was halted five times by the Nasdaq for volatility, still ended the day up 38 percent, its best day ever as a public company.
Its market cap jumped to nearly $28 billion before the paring the majority of its gains, at one point making it a bigger stock than 59 percent of the stocks in the S&P 500, a sign of just how big the hype has grown for pot-related plays on Wall Street.
It is now at least as large as 45 percent of the stocks that comprise the index. Tilray trading volume hit 30 million shares, tripling the stock's 30-day full-day average of 9.6 million shares. There are only 21 million shares of Tilray available for trading.
Nasdaq confirmed to CNBC the stock was paused according to predetermined rules on volatility. The wild trading continued after the market close with the shares down more than 11 percent after hours.
The gains were driven by bullish comments by CEO Brendan Kennedy, but traders said a so-called short squeeze played a hand in the big gains and wild trading.
"Cannabis is a substitute for prescription painkillers, prescription opioids, and so if you're an investor in a pharmaceutical company or you're a pharmaceutical company, you have to hedge the offset from cannabis substitution," the Tilray executive said Tuesday.
The chief executive argued that the same can be said for food and beverage companies. Aurora Cannabis has rallied 26 percent this week in Canadian trading after Canadian news service BNN Bloomberg reported Coca-Cola is in talks with Aurora to develop weed-infused beverages.