Lululemon Athletica cut its outlook for the second time this year following another quarter of declining sales in its Americas business.

The activewear retailer said Thursday it now expects annual sales to be $10.35 billion to $10.5 billion, down from its previous guidance of $11 billion to $11.15 billion. It also lowered its projection for earnings per share for the year to $9.48 to $9.73, down from $10.95 to $11.15.

The company said it is taking a prudent approach with its guidance because the challenging dynamics it has faced in recent quarters haven't gone away.

Lululemon plunges more than 18% in after-hours trading.

"We anticipated our plan would take some time to gain traction," said Meghan Frank, interim co-chief executive and chief financial officer. "But we expected a better response than we are seeing as we enter the second half of the year."

Shares slid 17% to $100.18 in after-hours trading. Through the close, the stock was down 42% this year.

Executives said second-quarter sales were dented by negative online narratives about the brand, a comment they also made in June following the company's first guidance cut of the year. Several product launches failed to meet expectations, as Lululemon lost more North American customers to competitors such as Alo and Vuori.

"The overall response to our product launches remains inconsistent, and we've continued to see pressure on the brand in both of our largest markets," Frank said.

Revenue declined 4% to $2.42 billion, below the $2.46 billion that analysts expected. Revenue in the Americas slipped 8%, while international revenue was up 4%.

Same-store sales dropped 9%, while Wall Street was projecting a 4.6% decline.

Lululemon is trying to sell more clothes for full price and without promotions. However, it had a greater-than-expected slowdown in sales of some of its core products, including leggings and women's tops, Frank said.

Profit fell to $329.2 million, or $2.92 a share, from $370.9 million, or $3.10 a share, a year earlier. Earnings included 86 cents a share from tariff refunds and associated interest, net of tax.

Lululemon said it expects third-quarter revenue to be $2.29 billion to $2.32 billion, which would be below analysts' forecast of $2.53 billion. It anticipates earnings per share of 93 cents to 98 cents.

The results come as Lululemon is about to welcome Heidi O'Neill as its new chief executive next week. Investors are hoping she could help steer the company towards a turnaround after a series of bad moments for the brand, many of which have played out publicly.

In the spring, Lululemon made peace with its founder Chip Wilson, who had spent years criticizing the company and trying to overhaul the board via a proxy fight. Wilson, who is Lululemon's biggest shareholder, settled with the company in the spring after a long negotiation process. He agreed to sign a nondisparagement agreement in exchange for the right to name two board directors.

After O'Neill was appointed as chief executive, shares dropped, as investors critiqued her tenure as a former Nike executive. Analysts say they want to see her stop expanding stores, focus on improving North American sales and refocus on core products and traditional color palettes.