Shares of Teva Pharmaceutical fell more than 18 percent in morning trading Thursday after the company reported lower-than-expected second-quarter earnings.

Teva missed estimates for both earnings per share and revenue, and interim CEO Yitzhak Peterburg blamed the poor performance on a saturation of the U.S. generic drug market.

"[Teva] experienced … greater competition as a result of an increase in generic drug approvals by the U.S. FDA," Peterburg said in the earnings release. He added that "customer consolidation" hurt sales in the U.S., before saying competition hurt new product launches, some of which were delayed in the recent quarter.

Earnings per share of $1.02 was 4 cents below what analysts surveyed by Reuters expected. Revenue also fell short of analyst forecasts by more than $300 million, coming in at $5.686 billion compared to the expected $5.718 billion.

Peterburg said instability in the Venezuelan bolivar had a material effect, reducing revenue by $183 million compared to the same quarter last year.

On June 28, Peterburg warned that the global health-care industry faces a "huge disruption," saying at the World Economic Forum that he believes "it will affect" the pharmaceutical industry.

Teva Pharmaceutical, headquartered in Israel, calls itself the largest producer of generic medicines. In specialty medicines, Teva has treatment for multiple sclerosis as well as late-stage development programs for other disorders of the central nervous system.

The pharmaceutical company lost its CEO on February 7 when Erez Vigodman resigned suddenly amid reports of a bribery investigation by the Israel Police. The biggest company in Israel, Teva allegedly paid bribes into the hundreds of millions of dollars and falsified documents in order to hide them.

Teva's stock fell more than 14 percent in pre-market, before continuing to decline after the market open. Shares of the company were down nearly 14 percent this year ahead of Thursday's open.