Until last year, the last new anthelmintic (dewormer) class that was introduced to the market was macrocylic lactones (i.e. Ivomec) by Merck in 1981. But since last year, two new sheep drenches have entered the pipeline: Zolvix® and Startect®.
Zolvix® (monepantel) was released by Novartis last fall in New Zealand. It is now available to producers in Australia, Europe, and South America. Startect® (derquantel + abamectin) was recently released by Pfizer. Currently, it is available only in New Zealand.
Both new sheep drenches represent new anthelmintic classes. They have different modes of action than current anthelmintics. Consequently, they are effective against worms that are resistant to other classes and combinations of anthelmintics.
When (and if) these anthelmintics become available in the United States is anyone's best guess. It is often too expensive for the drug companies to get approvals for drugs that have limited market potential.
Perhaps, the Minor Use/Minor Species Act will facilitate the approval of these two new drenches for U.S. producers. The purpose of the act is to find innovative ways to bring products for small populations to market and is designed to help pharmaceutical companies overcome the financial roadblocks they face in providing limited-demand animal drugs.