Side-effects only found after drugs hit the market

Keeping track of the potential side-effects of a new drug is a nightmare for the average GP in the UK.

Of course, we know that you can’t be certain a drug is safe until it’s been on the market for years and, even then, we can’t be sure that yet more side-effects don’t lie just around the corner. Serious side-effects – or adverse drug reactions (ADRs) as the medical profession calls them – are usually only discovered after the drug has been on the market for years anyway.

Now, a US study, the first to analyse the ‘black-box’ or side-effect warnings appearing in the standard American drug guide – the Physicians’ Desk Reference – recommends that GPs should avoid using new drugs if older, more established, alternatives are available.

If GPs have to use the latest drug, they should inform these patients of its limited life and safety record, and observe the patients closely. The study also suggests that the labelling should show prominently when the drug was approved, and any changes should also be highlighted and dated.

When a serious side-effect is discovered, the labelling of all other drugs in the same class should be reviewed as well. After all, new data for the drug’s performance may determine whether the GP prescribes it or not.

In the US, nearly 20 million patients took at least one of the five drugs that the country’s medical watchdog, the Food and Drug Administration (FDA), pulled off the market between September 1997 and September 1998. Three of those five drugs were new, having been on the market for less than two years. More important, says the study, seven drugs approved since 1993, and subsequently withdrawn from the market, may have contributed to 1002 deaths.

However, nothing will completely eliminate the risk of unexpected side-effects. ‘Innovative new therapies are important,’ say the authors, ‘but when safe and effective therapies already exist, any new drug should be considered a black box’ (JAMA, 2002; 287: 2215-20, 2273-5).