Do efficacy results obtained from randomized controlled trials translate to effectiveness data from observational studies for relapsing-remitting multiple sclerosis?

BACKGROUND: Randomized controlled trials are considered the gold standard in regulatory decision making, as observational studies are known to have important methodological limitations. However, real-world evidence may be helpful in specific situations. This review investigates how the effect estimates obtained from randomized controlled trials compare to those obtained from observational studies, using drug therapy for relapsing-remitting multiple sclerosis as an example. STUDY DESIGN AND SETTING: A systematic review of randomized controlled trials and observational studies was conducted. The primary outcome was the annualized relapse rate. Using (network) meta-analysis together with posterior predictive distributions, the drug-specific rate ratios from the network of randomized controlled trials were compared with those from the network of observational studies. RESULTS: Effect estimates from 26 observational studies showed greater magnitudes and were less precise compared to estimates obtained from 21 randomized controlled trials. Twenty of the 28 treatment comparisons between designs had similar rate ratios. Seven inconsistencies in observed rate ratios could be attributed to two specific disease-modifying therapies. CONCLUSION: In this case study, estimates from observational studies predominantly agreed with estimates from randomized controlled trials given their posterior predictive distributions. Multiple observational studies together may therefore supplement additional pivotal randomized controlled trials in relapsing-remitting multiple sclerosis, for instance facilitating the extrapolation of trial results to the broader patient population.

Interchangeability of generic anti-epileptic drugs: a quantitative analysis of topiramate and gabapentin.

PURPOSE: The objective of this study was to determine whether the so-called "shift" or "drift" problem might occur when generic anti-epileptic drugs are interchanged, and thus to assess if generic anti-epileptic drugs are interchangeable and can be used in an efficacious and safe way on the basis of their bioequivalence to one and the same reference product. METHODS: The bioequivalence of topiramate and gabapentin generics was evaluated. For proper interstudy comparison, individual exposure data (AUC and C(max)) for each bioequivalence study present in the registration dossier was normalized based on the absolute exposure data of one of two innovators. The exposure-normalized plasma concentration curves of the generic product arms between studies were compared, providing indirect evidence of bioequivalence of the different generics. Additionally, comparisons were made for generic-generic as well as innovator-innovator exchange based on absolute exposure data from individual bioequivalence studies. RESULTS: In almost all cases, estimated 90% confidence intervals of the AUC and C(max) ratios for generic-generic interchange were within the routine 80-125% criterion. When absolute, non-corrected exposure data were used for this interstudy comparison, in a number of cases 90% confidence intervals outside the 80-125% criterion were found upon interchanging generics from two studies. However, a similar pattern of 90% confidence intervals outside the 80-125% criterion was observed for the comparison of innovator arms, despite the fact that the innovator was identical in all studies. CONCLUSION: Our results strongly indicate that the so-called drifting problem upon generic-generic substitution does not result in important differences in exposure upon exchanging topiramate generics or gabapentin generics.

Antidepressants use in children and adolescents and the risk of suicide.

OBJECTIVE: Antidepressants use in paediatric patients has been linked with risk of suicidal behaviours. The aim of this paper, therefore, is to examine whether all antidepressants are associated with such risk. METHOD: All 22 paediatric short-term placebo-controlled trials of SSRIs and NSRIs that were submitted to European registration authorities by pharmaceutical companies were identified and examined for events related to suicidality, which were defined as suicide, suicide attempts or suicidal thoughts. Random effect meta-analysis was used to combine the information from all trials. RESULTS: No completed suicides were reported. However, for each compound there was at least one study with an increased risk for events related to suicidality in the active compound group. The overall OR for these events in the depression studies was 1.67 (95% CI: 1.05-2.65) and for anxiety 1.33 (95% CI: 0.33-5.35). CONCLUSIONS: Caution is called for in the use of all SSRIs and NSRIs in the paediatric population. Furthermore, in the absence of contradictory information, caution in the use of other antidepressants in this population should be exercised as well (e.g. tricyclic antidepressants).

Response to tricyclic antidepressants: independent of gender?

OBJECTIVE: The authors examined gender differences in response to tricyclic antidepressants. METHOD: A total of 30 randomized, placebo-controlled trials that included 3,886 patients (1,555 men and 2,331 women), submitted between 1979 and 1991 in order to obtain marketing authorization, were reviewed. Gender differences in response to treatment were tested in various multiple regression models using a variety of response definitions. RESULTS: Different response definitions all pointed to no gender difference in the efficacy of tricyclic antidepressants. The estimated effect size was similar for women younger and older than age 50 and for men. CONCLUSIONS: Tricyclic antidepressant response is independent of gender.

Amisulpride: is there a treatment for negative symptoms in schizophrenia patients?

In this article we report on a meta-analysis of the published studies of amisulpride conducted in order to demonstrate efficacy on primary negative symptoms in schizophrenia. Four placebo-controlled studies were conducted in patients with predominantly negative symptoms. In all studies a significant improvement was observed on the Scale for the Assessment of Negative Symptoms (SANS) in the amisulpride groups (50-300 mg daily) as compared to placebo. The improvement on the SANS was not accompanied by a simultaneous improvement on the Scale for the Assessment of Positive Symptoms (SAPS) or a decrease in extrapyramidal symptoms (EPS) in three of the four studies, indicating a genuine effect on primary negative symptoms. The overall analysis shows that the improvement on the SANS was accompanied by a small simultaneous improvement on the SAPS. Moreover, in the studies where depressive symptoms were measured, a significant improvement was also shown in favor of amisulpride. However, as the SAPS and the Montgomery Asberg Depression Rating Scale (MADRS) baseline scores were rather low, the improvement on both scales in favor of amisulpride is probably not responsible for the improvement on the SANS. A positive correlation was found between the severity on the mean SANS score at baseline and mean improvement at endpoint, and a surprisingly high success rate was observed in the placebo groups, indicating either that primary negative symptoms are not as persistent as had previously been thought, or that the concept of primary negative symptoms should be reconsidered. Probably amisulpride is efficacious on these nonenduring primary negative symptoms.