An ongoing dialogue on HIV/AIDS, infectious diseases,
March 10th, 2010
The Extraordinary Power of Placebo
Just published in the journal Neurology — not typically on my radar screen — is this remarkable study comparing pregabalin to placebo for HIV-related distal sensory peripheral neuropathy.
Here are the results:
At endpoint, pregabalin and placebo showed substantial reductions in mean Numeric Pain Rating Scale (NPRS) score from baseline: -2.88 vs -2.63, p = 0.3941.
Individuals with HIV-associated neuropathy achieved NPRS treatment effect size similar to those in studies of diabetic peripheral and postherpetic neuralgia. However, the placebo group in the current study had a much higher NPRS change than in the diabetic peripheral neuropathy or postherpetic neuralgia studies
In other words, the pregabalin here worked great, but the placebo effect was so gargantuan that the placebo was just as good.
Writing in Journal Watch: AIDS Clinical Care, the always-astute Abbie Zuger has a theory why this happened:
Notably, this study is not the first in which a treatment for HIV-related peripheral neuropathy has elicited an unusually high placebo response. The reasons behind that phenomenon would be extremely interesting to pursue — might HIV-positive individuals have greater faith in the power of medication than do others?
I think she’s on to something important here. After all, in how many other diseases can patients so directly link the medications they are taking to their own survival?
And we clinicians who practice HIV medicine should keep this in mind when prescribing medications to our patients. Strong mutual conviction that something will work — from both provider and patient — may well be a self-fulfilling prophecy.
Why not leverage this for all it’s worth?