A veterinary drug indicated for the emergency management of congestive heart failure in dogs and cats is disappearing from the market, with distributors claiming it's on back order while manufacturers are, so far, mum on the topic.

The medication is injectable furosemide, a loop diuretic commonly used to treat edema and hypertension in humans. In addition to treating heart failure in companion animals, veterinarians also use it to prevent or reduce exercise-induced pulmonary hemorrhage in racehorses, among other applications. 

While veterinarians can turn to human-grade IV furosemide, it's more expensive; one online pharmacy advertises the human version for $15 and the veterinary version for $8. Such discrepancy extends beyond pricing to include concentration and volume. For example, veterinary-grade IV furosemide is dispensed as 50 mg/ml in 100-ml bottles while the human version comes as 10 mg/ml in 2-ml vials.

News of the shortage has come to the attention of veterinary cardiologists, some of whom hesitate turning to compounding pharmacies for the drug because there hasn't been much experience in veterinary medicine using compounded injectable formulations of furosemide.

Wedgewood Pharmacy, one of the nation's largest veterinary compounding pharmacies, is preparing the medication during the back order.

Dr. Mark Kittleson, a veterinary cardiologist who teaches at the University of California-Davis School of Veterinary Medicine and is a Veterinary Information Network consultant, characterizes the value of injectable furosemide this way:

"It's what cardiologists live by. There really isn't any substitute," he says.

The VIN News Service, in its early investigations of what's driving the shortage, has not yet confirmed reports that the scarcity of injectable furosemide is related to the closure of Teva Animal Health last August, which some believe could have been making the medication for private labels. Company spokeswoman Denise Bradley could not be reached for comment.

Indications are also that the relocation of a manufacturing facility of Boehringer Ingelheim (BI), which markets furosemide by the brand name Disal and is believed to manufacture the drug for other private labels, has added to the shortage. While BI has confirmed that Disal is on back order, officials with the company have yet to clarify what's behind it.

The most popular veterinary brand of furosemide, Lasix, recently was renamed Salix in the veterinary market. Since the medication's introduction to U.S. veterinarians in the late 1960s, the name Lasix has become synonymous with furosemide, just as Google has become synonymous with Web search and Kleenex is synonymous with tissues. The branding change was due to trademarking issues related to the Aventis Pharmaceuticals' acquisition of the drug's human version from Intervet/Schering Plough Animal Health.

According to an online article posted in June by BloodHorse.com, "Salix will be uniformly manufactured in the same FDA-approved facilities, using the identical production outlines and raw materials."

Intervet spokeswoman Sharon Dilling is working on getting more information to the VIN News Service concerning the apparent shortage of Salix. 

Federal regulators have shed more light on the drug's availability to human medicine. On Aug. 10, the U.S. Food and Drug Administration updated an alert regarding a shortage of furosemide injectable. The online notice points to manufacturing delays and increased demand tied to three different brands, with one manufacturer indicating that its shortage could be relieved by October.

A Web bulletin from the American Society of Health-Systems Pharmacists further outlines the products affected from the same three manufacturers but cites that a fourth company has stopped producing the medication.

Phone calls from the VIN News Service to several distributors serving animal health have confirmed the shortage from their end.

"We used to carry three brands, but all are on back order," reports a customer service representative with Butler Animal Health. "It looks like they have been on back order for about two months."

Representatives with Midwest Veterinary Pharmacy, Vedco Inc. and AgriLabs made similar statements.

Veterinarians handling acute congestive heart failure without access to furosemide can turn to other loop diuretics such as torsemide and bumetanide, which can be administered parenterally. Dr. Mark Rishniw, a VIN consultant and veterinary cardiologist at Cornell University, notes that the veterinary profession has had little experience with either of these drugs because Lasix and other brands of furosemide have worked so well in the past.