RESUMEN
ABSTRACT: Large placebo responses often negatively affect randomized controlled trials within the pain area. Understanding different possible factors that influence the placebo response is therefore important. In this retrospective analysis, we hypothesized that a large variability in baseline pain score would predict a greater placebo response and analyzed the impact of the coefficient of variation, SD, and difference between the highest and lowest numeric rating scale (NRS) score at baseline on the placebo response. A total of 160 observations on placebo response from 3 controlled clinical trials with a crossover design were included in this study. In general, the placebo response was low with a mean reduction in pain intensity of 0.5 points (range -5 to 7) measured on a 0 to 10 point NRS, and only 15% were placebo responders as defined by more than 30% reduction in NRS pain score from baseline to the end of the placebo treatment period. We found no significant impact of baseline pain coefficient of variation, SD, or the difference between lowest and highest baseline pain score on the placebo response. Placebo response in one trial did not predict placebo response in another trial. A large placebo response was not associated with a large treatment response. In conclusion, in this retrospective data analysis, there was no impact of baseline pain variability on the placebo response in controlled clinical trials with a crossover design in patients with peripheral neuropathic pain.
Asunto(s)
Analgésicos , Neuralgia , Analgésicos/uso terapéutico , Estudios Cruzados , Método Doble Ciego , Humanos , Neuralgia/tratamiento farmacológico , Efecto Placebo , Estudios Retrospectivos , Resultado del TratamientoRESUMEN
ABSTRACT: Experimental data have suggested that in neuropathic pain, tricyclic antidepressants may work solely through a ß2-agonist action. The aim of this study was to test if the ß2-agonist terbutaline relieves painful polyneuropathy. The study was a randomized, double-blind, placebo-controlled and active-controlled, 3-way, cross-over trial among patients with painful polyneuropathy. The treatment periods were of 5 weeks' duration and were preceded by 1 week for washout and 1 week for baseline observations. The patients received terbutaline (5-15 mg), imipramine (30-150 mg), or placebo in a random order. Drug doses depended on age and metabolizer status. The change in total pain recorded from ratings in diaries (numeric rating scale [NRS] 0-10) was the primary outcome, and the change in rating of specific pain symptoms (NRS 0-10), patient global impression of change, and sleep disturbance were secondary outcomes. Forty-seven patients were randomized. The median score for total pain changed from NRS 6.4 to 6.1 from baseline to week 5 on terbutaline with an average effect during the treatment period as compared with placebo of 0.13 (95% confidence interval -0.12 to 0.38, P = 0.32). The median score for total pain on imipramine changed from NRS 6.6 to 4.8 with an average effect as compared with placebo of -1.17 (95% confidence interval -1.42 to -0.92, P < 0.001). Secondary outcomes were also unaltered by terbutaline but improved by imipramine. The ß2-agonist terbutaline has no effect in painful polyneuropathy. ß2-agonism seems not to be an important mechanism of action of tricyclic antidepressants in neuropathic pain.
Asunto(s)
Neuralgia , Polineuropatías , Antidepresivos Tricíclicos/uso terapéutico , Método Doble Ciego , Humanos , Imipramina/uso terapéutico , Neuralgia/tratamiento farmacológico , Dimensión del Dolor , Polineuropatías/complicaciones , Polineuropatías/tratamiento farmacológico , Resultado del TratamientoRESUMEN
The presence and magnitude of placebo responses is important for the outcome in clinical trials of analgesics. This explorative study aimed at identifying patients and trial-specific factors with impact on this response in randomized, controlled, cross-over trials in peripheral neuropathic pain. Data were derived from 7 trials and included observations on pinprick hyperalgesia, allodynia, and pain on repetitive stimulation. The studies were all performed by the same collaboration group in Denmark. Pain was rated daily using numeric 0 to 10 point rating scales (NRS) and placebo response was calculated as the difference in weekly average or median numeric rating scale from baseline to the last week of treatment. A clinically meaningful placebo response was defined as more than 30% reduction of pain on placebo. In 318 individual observations, the response was on average small (0.17 points, range -4.5 to 6). There was no significant impact on size of placebo response of trial-specific factors such as treatment sequence and chance of having placebo treatment in each period or of the patient-specific factors age, sensory signs, and pain symptoms. The findings were similar in patients having placebo in the first treatment period. There was no marked difference between patients with (n = 43) and without (n = 275) a clinically meaningful placebo response with respect to the patient-specific factors including frequency of sensory signs and symptoms. In conclusion, this study on cross-over trials in peripheral neuropathic pain found no robust impact of trial and patient-specific factors on the placebo response.
Asunto(s)
Neuralgia , Analgésicos/uso terapéutico , Estudios Cruzados , Método Doble Ciego , Humanos , Neuralgia/tratamiento farmacológico , Efecto Placebo , Resultado del TratamientoRESUMEN
Side effects such as myoclonus and tremor are rare when treating with selective serotonin reuptake inhibitors (SSRIs). We present a case where a patient with known liver cirrho-sis and in treatment with citalopram developed myoclonus, tremor and gait difficulties. The symptoms were reduced when the SSRI dose was decreased. In patients with unexplained movement disorders the usage of SSRIs should be considered as a cause. Furthermore, treatment with SSRIs should be carefully assessed in patients with reduced liver function.