MERLE BROWN

Last May I went to a pharmacist with one of the 31 million prescriptions issued in Britain each year for some form of anti-depressant, and picked up a month's supply of Prozac.

The three blister-packs of green and cream pills were the solution to a depression that had hit hard. My partner of three years had walked out of our home eight months earlier, and I had fallen apart. Susceptible to my emotions, I had taken a different anti-depressant, Seroxat, some nine years before; after a less-than-pleasant few months on that pill, I had been determined not to go down the chemical route again.

But, despite my best efforts, nothing would lift the black wave that had engulfed me. And so I sat in my doctor's surgery, sobbing and asking for help.

It is 20 years since Prozac was launched. The compound LY110141, now known as fluoxetine, was developed in 1971 by the global pharmaceutical company Eli Lilly, and was originally earmarked as a medication for high blood pressure. However, it wasn't successful in human trials, so new uses were examined. It was given to five mild depressives and found to cheer each of them up. By 1999, Prozac was providing Eli Lilly with more than 25% of its annual revenue.

Prozac is an SSRI - a selective serotonin reuptake inhibitor. Other such drugs have since hit the market - Seroxat among them - and each has had its detractors. A lot has been written about how easy it is to prescribe anti-depressants and what those who have depression should do instead of taking pills. Get out and walk or run, people say.

I couldn't lift my head off the pillow. For days on end I lay there, motionless, as the hours ticked by. On the advice of my brother and his wife, I went to a therapist for one session, but I felt that a deeper probing of my problems at that time would just make matters worse. I needed a quick fix, I admit it - and that's what Prozac offered.

Of course, it didn't really: it's no wonder drug. But it was the gentle shove I needed. And, in a way, it did become my personal wonder drug. Propelled by my Prozac, I re-entered the world. Two months on it, and I was out of the house. I was no longer crying every day; I was living my life again. I even met a new man. My boyfriend - we are still together - was the perfect spirit to my chemical tonic. Prozac didn't save me; he didn't save me. But the combination did. It's not for everyone, and perhaps at times it is too easily dispensed, but I can't bring myself to denounce Prozac.

It is a strange drug to be on. Initially you feel nothing; then, as it seeps into your system after a couple of weeks, there's a period of euphoria, almost mania, where everything just seems so good. My boyfriend took me camping on Skye. Camping! I hadn't done it since I was a kid and I loved every minute. I laughed for the first time in months. I picked up my discarded, half-written novel and found my writer's voice again. Only a few months earlier, I had spent days pacing up and down my flat, crying, sobbing, pulling at my hair, and, dare I say it, not caring if I lived or died. There were moments in my deepest depression when I wished I could close my eyes and not wake up. And the fact that taking Prozac removed those thoughts from my mind, I think, allows me to champion its cause for ever.

It has its side-effects, like any medication. For the first four months or so, my mouth was constantly dry because I was so dehydrated. Don't drink alcohol on it, my doctor instructed. When I did, I realised why she'd said that. It took just two glasses of wine to knock me out, and when I woke in the morning it felt like someone had smashed me over the head with a sledgehammer (and removed my memory). My doctor kept a close eye on me, and still does.

After almost exactly a year on the drug, I decided I was well enough to stop using it. And this is the crux: many Prozac users do become dependent on their pills. There is an element of fear in it: if I stop taking it, will I relapse into depression? Can I ever live without it?

A week and a half into my reduced dosage of half a dose a day, my boyfriend and I had an argument, and I got tearful and sobbed my heart out. Uh-oh, I thought, I'm not better at all. But I took a step back and realised it was more likely a mixture of over-tiredness, PMT and Prozac withdrawal that had caused me to break down, not a recurring depression.

Prozac is not a medication for manic depression, but for my own depression - a reactive bout of the clinical variety attributed to a "bad event" - it got me there. I do know, however, that having suffered from the illness two or three times in my life, I am susceptible to it. But I don't care. If I ever feel it clouding up my life, I know how to deal with it.

It has been said that some people think being depressed is "cool", and that celebrities use it like a status badge. If so, more fool them. If I had never needed to take Prozac in my life, I'd be happy. Believe me, as someone who has been there, there is nothing "cool" about depression.

Coming off my drug has, understandably, been difficult. But I'm down to half a regular dose of Prozac every third day now, and my withdrawal hasn't been too bad. The withdrawal from Seroxat all those years ago was one of the reasons I didn't want to go back on this type of drug again. Thankfully, Prozac hasn't been quite so bad. The main symptom I have is a sort of electric shock-type sensation, which occurred at times when I was on the drug, too. It's a sensation unlike anything else, and hard to describe. Extreme tiredness is another side-effect, as are the most vivid, exhausting dreams that have had me waking up feeling like I've run a marathon. But there is nothing that's too hard to cope with; nothing as bad as the way I felt before Prozac.

It is definitely with a strangely fond farewell that I leave Prozac behind. But it is with a large Prozac-assisted two-fingered salute that I bid goodbye to my depression. Prozac did exactly what it said on the tin.

A pill that has divided opinion worldwide
Twenty years after it was first prescribed, Prozac remains the most widely used antidepressant in history, prescribed to 54 million people worldwide.

It is used to treat conditions including depression, obsessive compulsive disorder and premenstrual dysphoric disorder (formerly known as PMT).

In the UK, between 1991 and 2001, antidepressant prescriptions rose from nine million to 24 million a year. Between 1996 and 2006, prescriptions for anti-depressants in Scotland doubled to 3.5 million, costing £55m.

Prozac has been dogged by claims that it can trigger suicide, not just in depressives but also in healthy volunteers. Some SSRI users have reported restlessness and agitation and a compulsion to commit violence on others or themselves.

However, according to most psychiatrists, the risk of not taking an antidepressant when suffering depression far outweighs any risks of taking one.

Eli Lilly has now launched a new anti-depressant called Cymbalta that also acts as a painkiller.