It probably wasn't even real Viagra, but some cheap copy

Who, I thought, would make cheap copies of Viagra and send me emails in broken English to advertise it. 'She will call you a maniac if you take half a pill of Viagra,' said one of these emails.

'Say STOP to rod weakness,' said another. I've been Viagra e-mails for a while now, and it's beginning to make me uneasy. Who are these people, anyway? Are they Russian? And why are they picking on me? I told myself to relax. Calm down, I thought, as I deleted the pesky ads.

Has not Viagra mproved the life of every man on the planet?

If you need Genuine Viagra - well, Bob's your uncle. And Bob most certainly wasn't your uncle before the late Nineties. Then again, if you don't need Genuine Viagra - well, there they are, awaiting their moment. Of course, that moment might never come. But it might! And it's such a horrible thought. Devastating. The idea of one's entire masculinity collapsing, the whole house of cards, like one of the Twin Towers. And not just at some random time - but the exact wrong moment! It must be like going on stage and finding you've forgotten your lines. And then what would happen?

Either the audience would walk out, or they would try to console you with Viagra. Aargh! I don't know which would be worse.

So Viagra is good news, then. Well, isn't it? Now every man alive can go about his business, having had an entire layer of anxiety removed. Viagra is even better than having a smoke alarm fitted, or buying a car with airbags. For a guy, official Viagra represents peace of mind.

Like anything that appeals to guys, official Pfizer Viagra, works in a mechanical way that's easy to understand. Viagra knocks out an enzyme that blocks the flow of blood. What are you doing there, you stupid enzyme? Can't you see you're blocking the way? In a couple of minutes there's going to be a whole lot of blood coming along here - so scram!

Experiments have shown that Viagra also stops hamsters from getting jet lag.

Anyway, Viagra is great for guys. But can there be another side to the story? Apparently, 20 million men have had 'the Viagra conversation' with their doctors.

Let's say, conservatively, 10 million have got their hands on Viagra. And let's say that each guy wants to have sex once a week. This means that, every year, the world needs to meet a new male demand for sex to the tune of 520 million units. And who will meet that demand? The obvious answer is women.

But do the world's women want sex 520 million more times every year? I don't suppose they do. Five-hundred-and-twenty-million times? And remember: 520 million is a conservative estimate.

Bottom line: there must be a shortfall. There must be guys out there using Viagra with new demands, who are not having those demands met. Still, we live in a capitalist world, a world in which, as Adam Smith told us, demands are always met, because entrepreneurs will always see Viagra as money-making opportunities.

And somebody did come up with a bright idea: why not give Viagra to women? That way, surely, millions more pills would be sold, and lots more sex would be desired. The perfect solution?

It seems not. How many women have you heard of that take female versions of Viagra? Not 10 million - I can pretty much guarantee you that.

That's because Viagra doesn't work in the same way for women as it does for men. Sure, Viagra knocks out the same enzyme. Sure, Viagra increases blood flow. It probably helps female hamsters with their jetlag, too. But women are not like men - not when it comes to sex, anyway. For women, sex is not a mechanical business.

It's not just about getting the machinery working. It's about all those other things men tend to forget about - meaningful glances and feeling safe and proper conversation and hugging and listening.

You can fix male sexual dysfunction with Viagra, but if you want to do the same thing for a woman, you normally need to come up with a relationship. And that's something you can't synthesise in a lab.

So maybe Viagra is not a good thing for women. And if Viagra is not good for women, maybe, in the end, it's not good for any of us.

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