Novartis Animal Health has ceased production of Interceptor, Sentinel and several other drugs manufactured in its plant in Lincoln, Neb., while the facility undergoes "process and compliance improvement activities," a spokesman for the company confirmed today. 

Mickey McDermott, head of communications for Novartis Animal Health in North America, could not immediately identify what other products are being impacted by the plant's temporary shutdown aside from Interceptor and Sentinel, both pet parasitides. He did not specify the type of modifications underway or whether they were prompted by the U.S. Food and Drug Administration (FDA), which regulates facilities that manufacture and process livestock feeds, pet foods and veterinary drugs and devices. 

Officials with the FDA's Center for Veterinary Medicine did not respond today to a query about whether the agency is involved in Novartis's process and compliance upgrades. 

McDermott noted that the changes are being made "voluntarily." The company hopes to resume its regular production schedule sometime in January. 

"We're hoping this will be very temporary," he said. 

So is Dr. Steven Hornstein. As a solo practitioner in Monroe Township, N.J., he dispenses 40 or 50 boxes of Interceptor, a broad-spectrum antiparasitic that contains milbemycin oxime, on a monthly basis.

"It's the main heartworm preventative I use, so this will impact me," Hornstein said. He plans on turning to Elanco's flea killer and heartworm preventative Trifexis, which contains spinosad and milbemycin oxime.

Trifexis is not a direct substitute for Interceptor or Sentinel, which contains milbemycin oxime and lufenuron. According to the label for Trifexis, serious adverse reactions have been reported following concomitant extra-label use of ivermectin, another broad-spectrum antiparasiticide, with spinosad alone, one of the components of Trifexis chewable tablets.

All three antiparasitics act as heartworm preventatives and have similar label claims when it comes to treating common intestinal parasites such as hookworms, roundworms and whipworms. Interceptor, administered via flavored tablets, is not designed to target flea and tick populations. Sentinel, also a flavored tablet, inhibits flea egg development but does not kill adult fleas or ticks. Trifexis targets adult fleas but is not marketed for tick prevention or protection.

Hornstein noted that he's received no communication from Novartis with news of the supply disruption. He found out from a colleague who alerted others via a post on the Veterinary Information Network (VIN), an online community for the profession, after her practice manager attempted to place an order for Interceptor.

Members of VIN have attempted to reach out to Novartis officials in search of clear answers about the supply issues. Thus far, their queries have gone unanswered. 

The most recent news releases featured on the Novartis U.S. website date back to 2009. It's unclear whether Novartis sent a "Dear Doctor" letter — a form of communication that pharmaceutical companies often use to alert medical professionals to changes concerning their products — to veterinarians.

"Would it be nice for the company to warn us? Absolutely," Hornstein said. "I'd like to get this information first, from them."

Editors Note: This article was amended from its original to include additional information about the antiparasitics featured.