Evidence Check 2: Homeopathy - Homeowatch

Evidence Check 2: Homeopathy 7Scientific plausibility18. Medical interventions are usually supported by explanations for how they work and thesame is true of homeopathy. Scientific explanations for a mechanism of action areimportant because they can lead to refinements of medicines: for example, new vaccinesfor viruses based on the known mechanisms of immunisation. Understanding amechanism of action can also enable the development of entirely new medicines: forexample, the persistent threat of resistance means that new anti-malarial drugs with novelmechanisms of action are continually required. 21 Our expectation of an explanation for amechanism of action is that it is both scientifically plausible and demonstrable. We should,however, add that, while we comment on explanations for how homeopathy works, it isnot a key part of our Evidence Check. Historically, some medical interventions weredemonstrably effective before anyone understood their modes of action. For example, after150 years of use, there is still debate about precisely how anaesthetics work. 22 It is moreimportant to know whether a treatment works—its efficacy—than how it works.Evidence of efficacyRandomised controlled trials (RCTs)19. Randomised Controlled Trials (RCTs) are the best way of determining whether a causeeffectrelationship exists between a treatment and an outcome. 23 Well designed RCTs havethe following important features:• randomisation: patients should be randomly allocated to placebo (dummytreatment) 24 or treatment groups—this ensures that there are no systematicdifferences between patient groups that may affect the outcome;• controlled conditions: aside from the treatment given, all patients should be treatedidentically, whether in placebo or treatment groups—this excludes other factorsfrom influencing the outcome;• intention to treat analysis: patients are analysed within their allocated group even ifthey did not experience the intervention—this maintains the advantages ofrandomisation which may be lost if patients withdraw or fail to comply;• double blinding: patients and clinicians should remain unaware of which patientsreceived placebo or treatment until the study is completed—this eliminates thepossibility of preconceived views of patients and clinicians affecting the outcome;and• placebo controlled: if there is no appropriate alternative treatment against which tocompare the test treatment, the intervention under consideration is tested against adummy treatment to see if the intervention has any benefit or side effects.21 T Wells, P Alonso and W Gutteridge, “New medicines to improve control and contribute to the eradication ofmalaria”, Nature Reviews, November 2009, vol 8: 87922 “Anaesthesia”, BBC Medical Notes, 2 May 2006, news.bbc.co.uk23 “Understanding controlled trials: Why are randomised controlled trials important?”, BMJ,1998, vol 316, p 20124 Placebos and the placebo effect are considered at paragraph 30 and following.