More experiments are being carried out on animals, despite genetic, biochemical and physiological differences with humans
Andrew Knight, guardian.co.uk, Thursday 12 July 2012
When a dog with a life-threatening uterine infection was recently carried into my veterinary practice, I was confident we could save her. Following a rapid infusion of intravenous fluids and antibiotics, I performed emergency surgery. Partly because of the drugs she was given, “Annie” recovered well. I had the luxury of knowing they had all been tested on other animals of the same species, and were unlikely to inadvertently cause any harm.
Unfortunately, my brother does not have that luxury. He works as a resident in a hospital emergency department, and although the drugs he uses have also been thoroughly tested on animals, this doesn’t provide quite the same level of comfort. It is one of the tragedies of modern medicine that adverse reactions to pharmaceuticals cause thousands of potentially avoidable deaths.
Modern drugs are more carefully studied than ever before. After lengthy tests on animals, those considered safe, and potentially effective, enter very limited human trials. About 92% are then weeded out and deemed unsafe or ineffective.
The remaining 8% are some of the most closely scrutinised compounds on the planet. You might be forgiven, therefore, for assuming they are safe. But at least 39 studies over three decades have ranked adverse drug reactions as an important cause of hospital deaths. Only heart disease, cancer and stroke are more reliably lethal.
The strains placed on healthcare systems and public finances should not be underestimated. Adverse drug reactions account for some 4% of UK hospital bed capacity, at an annual cost of around £466m.
I analysed in detail 27 systematic reviews examining the contributions of animal experiments to human healthcare. Their outcomes are remarkably consistent. Animal studies rarely contribute to the development of clinical interventions effective in human patients.
It’s not hard to fathom why. Animals have a plethora of genetic, biochemical and physiological differences that alter disease progression, drug uptake, distribution and effect. Stressful environments and experiments are common, and distort outcomes. Additionally, numerous studies have revealed scientific flaws in the design of many animal experiments.
Yet despite all this, figures just released by the Home Office reveal that 3.8m scientific procedures using animals were commenced in Great Britain last year – the greatest number since current records began, 25 years ago. Seventy-one per cent did not use anaesthesia of any kind. Although painkillers are sometimes given, often they are not, partly owing to concerns this may affect the experiment’s outcomes.
Fortunately, the future appears brighter. Sophisticated software is increasingly able to predict drug concentrations in different tissues, and toxicity or other biological effects, based on chemical structure. Batteries of molecular tests and cell cultures allow detection of a widening range of toxins, for a fraction of the time and cost of traditional animal tests. DNA microarrays (“gene chips”) increasingly link changes in genetic expression to specific toxins, allowing earlier detection. Stem cells hold enormous promise for both therapeutic and research applications, because of their potential to differentiate into a wide range of functional tissues.
Such technological advancements will not cure all human ailments, nor completely eliminate treatment risks. They do, however, offer the greatest hopes of producing safe and effective pharmaceuticals and other clinical interventions. It is towards such technologies that our resources must be invested, rather than animal tests of increasingly questionable scientific and ethical merit.