Teva Pharmaceuticals (TEVA - Get Report) shares dropped in midday trading Monday, following a tumultuous couple of days of trading in Tel Aviv.

Teva shares dropped 37% on Monday in Tel Aviv following 22% drop on Sunday, Aug. 6, the start of the trading week in Israel. Shares have lost 47% since the start of the year.

The Israel-listed generic pharmaceutical maker on Aug. 3 cut its full-year guidance and slashed its dividend 75% owing to weaker U.S. markets and the ongoing political turmoil in Venezuela. Interim president and CEO Dr. Yitzhak Peterburg said in the earnings release that Teva experienced accelerated price erosion and lower volume in its U.S. generics business due to "customer consolidation, greater competition as a result of an increase in generic drug approvals by the U.S. Food and Drug Administration, and some new product launches that were either delayed or subjected to more competition."

Teva's U.S. listing was down the most active stock in Monday morning trading, falling 7.96% to $18.96. Fellow generics maker Mylan Inc. (MYL - Get Report) was also active, losing 2.92% to trade at $31.95 midday.

On Friday, Fitch Ratings downgraded Teva's issuer default rating to 'BBB-' from 'BBB' with a negative outlook, noting that the company is "facing significant operational stress at a time when it needs to reduce debt and leverage" from its acquisition of Allergan plc's AGN generic drug business for $33.4 billion in cash and $5.4 billion in stock. The deal was completed in August 2016.

- Armie Margaret Lee contributed to this report.

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