At my bus-pass holding time of life, you don't often come across a word whose meaning you could no more guess at than a street sign in Tokyo. It happened to me when trawling Hansard the other day. The word was 'biosimilars'.

All right, I realise that you know all about biosimilar drugs. But when I rang a friend who does advanced level scientific research in the NHS, even he had to think for a moment or two before conceding: "Ah, yes, recombinant molecules - this is an emerging issue.''

And so it seems to be. Biosimilars are first cousins of generic drugs, the kind that big pharmaceutical companies manufacture under different names (and cheaper) when a drug comes off patent after 20 years. Except that they're more complicated - and that's a problem.

Whereas conventional generics are relatively easily copied exercises in chemical synthesis - such copies can often be developed for as little as£500,000, peanuts compared with the original research - biological drugs consist mainly of protein. They are very large molecules that can twist and kink like tangled wool.

In doing so, they can interact in different ways. I hope you're still following me. That means that the end copy of a biological drug is often not quite the same as the original; nor will its effect on patients be quite the same. Similar, but not the same; sometimes dangerous. We're talking safety here. Now have I got your attention?

There's a lot at stake here, as Brian Iddon, Labour MP for Bolton South East and an academic chemist, explained when he raised the attendant problems in the Commons the other evening.

Some 200 such drugs are now produced by the biotech industry. They help to treat cancers, AIDS, heart disease, diabetes and rare gene or neurological disorders, benefiting an estimated 325 million patients.

So far so good. But this fledgling new technology is not so new. Five of its early products are now out of patent, more will follow. Obviously, biosimilars - a name preferred over "biogeneric" by both UK and EU regulators - are extensively tested. It can cost£5m-£20m to do so: 10 or 20 times as much as for ordinary generics. But since they cost more, so are the potential savings to the NHS in the generic route. Generics, incidentally, are regulated nationally; biosimilars by Brussels, which gave its first authorisation to a drug called Omnitrope - it treats growth problems in children and adults - just two years ago. Six more have since had the OK.

So far still so good. But Dr Iddon, a busy 67-year-old who favours legalisation of both brothels and cannabis, chaired a panel of peers and MPs last winter to promote a 12-point safety plan which he put this month to health minister Dawn Primarolo. Hence the debate.

Among the recommendations that the minister seemed happy to promote too are that biosimilars should only be dispensed by the specific brand name, not their generic name, and that automatic substitution of other (cheaper?) brands should not be allowed. Some EU states have already done this.

Why? Back to my earlier point. Different processes can produce different products. Some products, some individual batches even, can produce adverse reaction in some patients. The British National Formulary should deploy the existing black triangle - used to denote drugs new to the market - on all biosimilars as their use moves beyond hospitals into the primary care world.

Pharmaco-vigilance, via the voluntary yellow card system that reports adverse reactions, should be strengthened and accompanying literature made more detailed. There should be public awareness campaigns and an EU-wide database. Ms Primarolo seemed to agree with most of this, though she also pointed out that drug substitution is not meant to happen without the consent of the prescriber.

I should say that the British Generic Manufacturers Association wasn't called to give evidence to the (informal) Iddon panel and regards the evidence provided as "not balanced". But I've done some checks, not least on Dr Iddon, who is one of those MPs with no outside financial interests. But money as well as better health is involved here. Europe hopes to get a beat on the US and Japan in all sorts of biotechnologies. Scary? Of course. But overall, no. Ain't science wonderful?