Prozac for Your Dog
Friday, March 30, 2007

A new canine version of Prozac will soon be available. It is just the latest in pet-specific drugs, as pharmaceutical companies increasingly chase this lucrative market. 

Anxiety-ridden dogs that go berserk when left alone by their owners will soon have a new treatment option--a reformulated version of the antidepressant Prozac, known generically as fluoxetine. To be marketed under the name Reconcile by Indianapolis-based drugmaker Eli Lilly, the drug is chewable and flavored with a doggie-delectable zing. It is the latest in a string of recently approved canine drugs, reflecting the growing market for pet pharmaceuticals.

The U.S. Food and Drug Administration approved Reconcile in February after clinical tests in dogs showed it significantly improved symptoms of separation anxiety, a problem that strikes 10 to 20 percent of canines with varying severity; dogs affected may bark, chew household items, or urinate in inappropriate locations when left alone. The drug, which will go on the market in April and will be sold along with a behavior modification program, is the first product introduced by a new division of Lilly devoted entirely to pets. 

Most drugs used for companion animals, as the pharmaceutical companies refer to pets, are human drugs that veterinarians prescribe off label. The cost of drug development is so high that few companies are willing to spend the money it takes to develop a canine-specific drug, or to run clinical trials testing human drugs for dogs or cats. But as more and more Americans view their pets as family members that is changing, and a new market is opening up: medications are being reformulated and sold in animal-friendly forms, and drugs that never quite made it through the human testing process are being revived.

"I think the human-animal bond has changed in the last few years," says Dawn Boothe, a veterinary internist and clinical pharmacologist at Auburn University in Auburn, AL. "People are starting to say, 'My animal is a member of the family, and I am willing to pay the cost of drugs that were developed for humans.' I think the pharmaceutical companies have picked up on that."

Two other pet drugs were approved early this year: the first diet drug for dogs, Slentrol, and the first motion-sickness drug for dogs, Cerenia. Both are being sold by New York-based Pfizer. Unlike Reconcile, neither drug has ever been prescribed for humans. Dirlotapide, the generic form of Slentrol, was originally tested for human use, but its side effects were deemed intolerable. (Compounds in the same class are being tested for their cholesterol- and triglyceride-reducing properties in humans.) 

Veterinarians are excited about the prospect of drugs that have been tested specifically in pets. "Prozac is a drug we've used for years," says Boothe. "But having it approved in dogs gives us a level of confidence regarding safety and efficacy in that species." Although scientists have tested different drugs in cats and dogs, Boothe and others say it has been difficult to get pharmaceutical companies interested in developing them. Nicholas Dodman, an animal behaviorist and veterinarian at Tufts University in Medford, MA, says a drug currently used to treat dementia in humans is helpful in treating an animal form of obsessive-compulsive disorder, but so far no pharmaceutical company has opted to develop it for the pet market. 

Lilly's companion-animal division is testing molecules from its vast library of compounds to treat obesity and other conditions in pets, a process they hope will produce some returns on the original investment in those molecules. "Even if you assume only two million of the dogs with anxiety disorder get treated," says Dodman, "with owners paying $50 per month, that's a viable market." 

By Emily Singer

Fluoxetine (Prozac®, Reconcile®)

Behavioural disorders in dogs and cats are common causes for veterinary visits. Behavioural problems are also a frequent reason for euthanasia of pets, especially when unacceptable or dangerous animal behaviour is involved. 

Recently, veterinarians have begun placing increasing emphasis on training and behaviour modification, and animal behaviour specialists have adopted drugs used in modifying human behaviour for animal use. Fluoxetine is one of these drugs. 

Fluoxetine is an antidepressant that is used to treat depression in people. 

This drug increases serotonin levels in the brain. Serotonin is a chemical that facilitates transmission of "messages" among brain cells. 

Fluoxetine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.

This drug is not approved for use in animals by the Food and Drug Administration (FDA) but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names

This drug is registered for use in humans only.

Human formulations: Prozac® (Dista) and various generic equivalents

Veterinary formulations: Reconcile® (Lilly) - chewable flavoured tablet. 

Uses of Fluoxetine

Fluoxetine is used for behaviour modification of dogs and cats. Reconcile® is labelled for dogs with separation anxiety. 

Common uses for fluoxetine include treatment of aggression and obsessive-compulsive disorders in dogs and cats. Fluoxetine can also be used to treat itchiness that is unresponsive to more conventional therapies. 

Precautions and Side Effects

While generally safe and effective when prescribed by a veterinarian, fluoxetine can cause side effects in some animals.

Fluoxetine should not be used in animals with known hypersensitivity or allergy to the drug. Fluoxetine is contraindicated in animals with a history of seizures. 

Fluoxetine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with fluoxetine. Such drugs include drugs classified as monoamine oxidase inhibitors (selegiline), diazepam, phenylbutazone, digoxin or buspirone.

Side effects associated with fluoxetine include lethargy, panting, hyperactivity, shaking, restlessness, excessive vocalization, aggression and temporary lack of appetite. Gastrointestinal upset may also occur. 

When large quantities of fluoxetine are ingested, pets may seizure. Overdose should be promptly treated by your veterinarian. 

How Fluoxetine Is Supplied

Fluoxetine is available as 10 mg, 20 mg and 40 mg tablets or capsules.

It is also available in a 20 mg/5 ml liquid form.

Reconcile® is available as 8, 16, 32 and 64 mg chewable tablets. 

Dosing Information

Medication should never be administered without first consulting your veterinarian.

For dogs, the dose of fluoxetine is 0.5 to 1 mg per pound (1 to 2 mg/kg) given every 24 hours, orally.

For cats, the dose is 2 to 5 mg per cat once daily.

The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance. Pets must receive fluoxetine for 6 to 8 weeks before it can be determined that the medication is ineffective.

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