Pfizer Animal Health plans to continue to manufacture its brand of butorphanol tartrate, a staple drug among many in the veterinary profession that the company markets as Torbugesic.

The assertion, made to the VIN News Service today by Dr. Mike Wallace, group director of veterinary services with Pfizer Animal Health, is designed to allay fears that the drug is on “indefinite back order.” While Wallace confirms that there are manufacturing challenges tied to the drug, he did not provide details of them.

“This issue will be relieved shortly,” Wallace promises. “We are not discontinuing the drug. My impression is that there will be some shipments that will go out this month, and that this challenge stems from the time that we acquired Fort Dodge.”

Pfizer acquired the license to manufacture and sell Torbugesic — a synthetic opiate agonist-antagonist structurally related to morphine — with its 2009 purchase of Wyeth and its subsidiary Fort Dodge Animal Health. Fort Dodge received the U.S. Food and Drug Administration’s (FDA) approval to manufacture the veterinary formulation in 1994.

Torbugesic is licensed for use in horses as well as dogs and commonly used for pain relief and sedation in combination with certain α2-adrenoceptor agonists. The controlled drug is also used to alleviate coughing in dogs and cats.

Earlier this week, veterinarians began reporting their troubles accessing the drug on the Veterinary Information Network (VIN), an online community for the profession and the parent of the VIN News Service.

Reports surfaced citing second-hand news from distributors stating that Torbugesic might be leaving the market. The drug is widely used as a sedative and analgesic in dogs, cats and horses.

VIN members state that they’ve had a hard time purchasing 2 mg/ml and 10 mg/ml versions of the product, claims that the VIN News Service confirmed with calls to several veterinary distributors whose customer services personnel reported that the supply has run dry from their ends.

Dr. Richard Headley considers Pfizer’s commitment to Torbugesic good news for the profession. The companion-animal practitioner in Indiana stocked up on a generic version of the drug from Lloyd Laboratories upon hearing news of a potential back order. In a pinch, he might switch to using morphine, he says. “I use butorphanol a lot, more as a tranquilizer than as an analgesic,” Headley says. “When you combine it with Dexdomitor, it’s super nice for minor procedures. In dogs and cats, this drug covers only very mild pain and is short-acting as an analgesic.”

Intervet/Shering Plough Animal Health also markets butorphanol tartrate under the brand name Dolorex, though the VIN News Service could not reach officials concerning the drug's availability.

A handful of human-based manufacturers or relabelers — companies that are licensed to sell the product under their own brand name — market the drug in injectables or intranasal sprays, according to the FDA's Orange Book.

Veterinarians report to the VIN News Service that the 2 mg/ml and 1 mg/ml forms common on the human side render the drug cost prohibitive, especially when 10 mg/ml forms are needed to treat horses.

Doug Kemp, Pharm D and a VIN consultant, states otherwise.

“You just have to pass those costs on to the client,” he says, while researching the drug’s availability at Athens Regional Medical Center, where he works in the hospital's pharmacy department. “It’s not even showing up as a back order situation on the human side. Sometimes you just have to be creative about where to look for it.”
 
Dr. Rachael Carpenter hopes the supply situation doesn’t come to that. In horses, the drug is frequently combined with xylazine or detomidine for pain relief and sedation.

“There aren’t a lot of other opioids that we can use,” explains Carpenter, an equine practitioner in New York and VIN anesthesia consultant. “This drug is nice because you can give a horse some analgesia, and it won’t cause the excitement and pacing that are side effects with other drugs.

“We use this in almost every sedation that we do and for pre-anesthesia,” she adds. “It would be a real problem for us if we couldn’t access it.”