| Figure
2.1: Side Effects Can Bias Patients Towards Spurious Reports
of Efficacy |
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| Pain
intensity vs. time in a parallel group comparison of amitriptyline
(mean dose 65 mg/day), lorazepam (2.4 mg/day) and lactose placebo
in patients with post-herpetic neuralgia. Both active drugs
but not lactose placebo produced moderate to severe sedation
in all patients. Amitriptyline was superior to the inert placebo,
reaching statistical significance in week 6. Patients taking
lorazepam initially reported pain reduction, during the time
in which sedation was most pronounced, but this effect dissipated
after the first few weeks. It is possible that patients who
noted sedation thought they were on a strong analgesic and that
this belief biased them towards reporting pain relief. To improve
blinding and reduce this potential bias in subsequent studies,
we have used small doses of lorazepam and benzotropine, other
drugs to mimic sedative and anticholinergic side effects of
experimental medications ( From Max et al., 1988a). |
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