Fluoxetine hydrochloride (3-(p-trifluoromethylphenoxy)-N-methyl-3-phenylpropylamine HCl) was first described in a scientific journal in 1974 as a selective serotonin -uptake inhibitor. It was licenced for use in the treatment of depression in Belgium in 1986 and the USA in 1987. Before its launch, to introduce it to the public, its manufacturer Eli Lilly funded eight million brochures (“Depression: what you need to know”) and 200 000 posters. It would become one of the best selling pharmaceuticals of its age; by 1992 annual sales had reached US$1bn and by 1995 they had doubled to US$2bn. In 1999 ‘Prozac’ – the trade name of fluoxetine – was named on of the ‘Products of the century’ by Fortune magazine.

The impact of the drug is hard to overstate, both in terms of the culture of the treatment of mental health disorders and in Western society at large. Prior to the introduction of fluoxetine antidepressants had a reputation of having side effects and were cautiously prescribed as they were toxic in overdose. Fluoxetine, on the other hand, was relatively benign and its introduction practically created a market in drugs for mood problems that could be safely prescribed to anyone who wanted them.

Other SSRIs followed in fluoxetine’s wake and the result has been an explosion in the diagnosing of depression and the prescribing of antidepressants. This is all the more incredible when one considers that the revenue from antidepressants sales in 1975 was US$200million and the market was considered to be saturated. ‘Prozac’ has since entered the popular lexicon and spawned its own sub-genre of literature. Of these perhaps the best known is Prozac Nation, a bestselling – but in my view rather tedious – memoir of mental illness written by Elizabeth Wurtzel.

There have been some hiccups along the way. Fluoxetine doesn’t have as few side effects as originally thought and, amongst those who are prescribed it, anorgasmia is quite common. Nausea is often experienced initially and it can sometimes increase rather than reduce anxiety. There have been concerns about other SSRI drugs, notably paroxetine, increasing suicide risk in young adults and in 1989, Joseph Wesbecker shot and killed eight people and injured 12 others in Kentucky before killing himself. More recently a meta-analysis of 35 clinical trials of four antidepressants including fluoxetine concluded that the action of the medications was not clinical significance for any patient who was not severely depressed. (see July 2018 note below)

In 2007 Eli Lilly began to market fluoxetine for dogs under the name Reconcile. In this incarnation it’s chewable, tastes like beef and is intended to treat something called ‘canine separation anxiety’. This disorder amounts to a set of behaviours displayed by a dog when being left alone for too long. A dog so affected may urinate in inappropriate places or chew furniture. At the time of launch Lilly said that their research showed the up to 17% of dogs suffered from this behavioural disturbance. Reconcile comes in a once a day chewable beef flavoured capsule.

I don’t know much about dogs, but other people seem to really like them. I’ve been trying to think about what antidepressants for dogs tells us about ourselves. Many people see dogs as part of their families and as such project onto them human attributes. In their advertising Lilly avoid suggesting that Reconcile is a treatment for ‘canine depression’ but other articles written at the time of Reconcile’s launch are not so careful, here in the Times:

In Britain, research among pet-owners carried out for Sainsbury’s Bank in 2003 indicated that 632,000 dogs and cats had suffered from depression in the previous year.

Nearly three times as many pets had suffered from behavioural problems that which could be linked to depression, often resulting in the animal damaging its home or becoming moody or aggressive, according to the research.

The experience of a human disease such as depression involves complex human attributes such as thoughts, emotions and language. To suggest that we can extend the concept of a specific human mental illnesses such as depression to dogs is to stretch the paradigm almost to breaking point and shows at once how loosely lay people apply the concept and how engrained widespread mental illness it is in everyday thinking.

Not that this association will worry the pharmaceutical companies. Marketing antidepressants to dogs tacitly encourages dog owners to consider that their dogs have mental health conditions previously described in humans and this can only be good for sales. Many pharmaceuticals develop mission creep whereby manufacturers endeavor to win them licences to allow their use to treat disorders distinct from those for which they were initially licenced. Initially cleared for depression only, Fluoxetine is now used for anorexia and bulimia nervosa, obsessive compulsive disorder, panic disorder, premenstrual dysphoria and generalized anxiety disorder. Viewed in this light, the launch of Reconcile, and fluoxetine’s crossing of the species barrier, is just part of the drugs product lifecycle.

This is not to say of course that fluoxetine doesn’t have its uses for animals. In similarity to human subjects it may have impressive effects in some, moderate for others and no effect for a substantial number. The emphasis is on the problem being in the dog and nowhere else, just like in humans.

Links:

Prozac for your dog – Technology Review 2007

Eternal Sunshine – Observer May 2007

Emotions in animals – Wikipedia

(July 2018 note – the back and forth about whether or not antidepressants work has run and run since I wrote this. The most recent paper is Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis Cipriani et al)