Medical Matters: When we are prescribed a modern drug, the possibility of it not working does not generally cross our minds, writes Dr Muiris Houston.
This is partly because we perceive modern medicine to be reliable and partly because we rarely see other modern technologies fail. Advice to "take one three times a day for a week" subliminally translates as "I'll be recovered by the end of the week". But drugs are fallible, and there is growing evidence that treatment regularly fails.
The potential causes for failure are a complex set of social and medical factors. Was the diagnosis wrong? Did the doctor pick the wrong drug or prescribe an incorrect dose? Has the patient forgotten to take the tablets at the right time or not completed the course? Could the drug be less effective than the clinical trials on which its approval was based?
In reality, treatment can fail at every step of the chain from drug development to patient behaviour.
One of the biggest causes of drug failure is the development of an adverse reaction. Even though these are not usually fatal, they are, according to research in the United States, among the top six causes of death. More common adverse reactions, such as nausea, headache, diarrhoea and dizziness, mean people stop taking medication - and if they don't let their doctors know, it is another treatment failure.
A recent study of patients' experiences in different health systems, published in the journal Health Affairs, found that one in six patients in the UK stopped taking medicines because of side effects but neglected to tell their doctors. About 20 per cent of the chronically ill patients in the study said they had suffered as the result of a medication error in the past two years. Overall, for 9 per cent of patients, the mistake had serious consequences.
In an editorial in the New England Journal Of Medicine last month, Prof William Tierney of the Indiana University school of medicine wrote about "the troubling issue of adverse drug reactions". He pointed out that side effects are more common in older people and in those with severe chronic conditions who take multiple medications. In a key comment, he says: "Reducing the number and severity of adverse effects of drugs will require vigilance and co-operation of doctors, pharmacists and other healthcare professionals. Using electronic medical systems can help this happen by reminding the providers which drugs a patient is taking and which side effects to look out for."
And Prof Tierney calls for a study of what he terms errors of omission - missed opportunities to prescribe appropriate medication. "They may be even more common and the adverse effects of overlooking such opportunities may be huge," he says.
A week later, across the Atlantic, the British Medical Journal pointed out that of the five best-selling medicines globally in 2001, only two were recognised as the first choice of drugs in their class. The authors, Profs Albert Figueras and Joan-Ramon Laporte of the World Health Organisation Collaborating Centre for Research and Training in Pharmacoepidemiology, at the University of Barcelona, outline other evidence that prescribing patterns are far from optimal. They also focus on the role of the pharmaceutical industry and drug regulators in driving both the methods and the obligations of medical research.
Clinical trials are designed to evaluate drugs rather than patients or diseases, they say, warning that market authorisation seems to be granted on the basis of superiority over placebo, or dummy pill, rather than on the basis of relative efficacy and cost benefit.
Profs Figueras and Laporte are concerned that although the true risk-benefit ratio depends on the circumstances in which drugs are used, regulatory bodies tend to assess the quality and safety of medications "as if these were independent of the way and the context in which drugs are prescribed, dispensed and used".
It is an interesting and evolving debate that should not be confined to the medical profession. The voices of patients, regulators, pharmacists and others must be heard. Otherwise, many drug therapies run the risk of being devalued and distrusted by the people they are designed to help.