For drug manufacturers, the hurdles constantly get higher.

Patients demand drugs that work effectively but which are targeted so precisely that they have no side-effects. The pharmaceutical industry would like us to believe that such products are possible, but there is hardly a drug on pharmacists’ shelves that does not have at least one undesirable side-effect.

Some of the cosiest and most familiar drugs are among the worst offenders. Take aspirin. We all do.

This centenarian is a genuine lifesaver, with a near-miraculous list of battle honours. It is effective against pain, but more aspirins are swallowed to protect against heart disease than headaches. Worldwide, more than 60 billion doses are taken every year.

Yet if it were invented today, aspirin could never be marketed. Its most dangerous side-effect is damage to the stomach lining, causing ulcers and bleeding. In under16s, it can trigger a rare but potentially fatal condition, Reye’s syndrome.

No drug with two such damaging side-effects would get far in today’s risk-averse world. Yet it is impossible to deny that, overall, aspirin has done far more good than harm. By expecting drugs to be completely safe we are throwing away potentially valuable products too readily. Whenever new safety rules are introduced, costs rise and it becomes less and less profitable to produce drugs that have a limited market.

So people with rare diseases suffer. “Orphan drug” designations, whereby companies are given incentives to develop less profitable drugs, may help a little but the cost pressures inevitably drive companies to seek big-market drugs, the only way they can get their money back.

The problem then is that a rare side-effect may loom large simply because of the huge number of people taking the medication.

It looks awful if thousands of people suffer side-effects and join in class actions, but if tens of millions are taking the drug the numbers suffering may be only one in a thousand or less. The other 999 are alleviating their symptoms and enjoying life.

Side-effects of drugs for treating depression are especially tricky to assess. There is evidence that they may increase suicidal thoughts, if not actual suicide, among adolescents. This may mean that teenagers plunged into gloom are lifted sufficiently by the medicine so that they see the possibility of controlling their lives once more. Thinking of suicide could be a sign of improvement.

If every drug is to be assessed for suicidal thoughts, it creates another barrier, another set of costs, and another reason for rejecting promising medicines because of a side-effect that may be tiny when compared with potential benefits.

The reductio ad absurdum of the search for complete safety is stasis. No new drug will ever be approved because fear has paralysed innovation. Everybody will lose. There will be no new medications, and we will be forced to fall back on those approved in earlier times when standards were lower. So by seeking perfect safety we will end up with drugs that are actually less safe, but familiar.

It’s enough to give you a headache. I’d recommend an aspirin.

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