Study design randomized trials

Anticonvulsants, especially topiramate, and serotonergic drugs, especially ondansetron, show promise in initial, but well-designed, randomized controlled trials.43 Further studies are needed. Buspirone is well studied, but results are inconsistent. 

The question whether lutein and zeaxanthin can contribute to lowering the risk for AMD cannot be answered unequivocally by epidemiological studies. Only randomized controlled trials (RCTs) during the course of which xanthophylls are supplemented in a double-blind, placebo-controlled, and randomized manner, and in which results are evaluated according to clear predefined efficacy criteria (Seddon and Hennekens 1994) have the potential to provide definitive answers. The specific long-term time-course and intricate nature of AMD make the design of such studies difficult, however. 

Quality of evidence I, evidence from >1 properly randomized, controlled trial II, evidence from <1 well-designed clinical trial, without randomization from cohort or case-controlled analytic studies (preferably from >1 center) or from multiple time-series III, evidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees. 

II at least 1 well-designed clinical trial, not randomized, or a cohort or case-controlled analytical study, or from multiple time series, or from dramatic results of an uncontrolled trial III opinions of respected authorities... 

Initial therapeutic exploratory studies may use a variety of study designs, including concurrent controls and comparison with baseline status. Subsequent trials are usually randomized and concurrently controlled to evaluate the efficacy of the drug and its safety for a particular therapeutic indication. Studies in Phase II are typically conducted in a group of patients who are selected by relatively narrow criteria, leading to a relatively homogeneous population, and are closely monitored. 

The Canadian Task Force categorized the quality of evidence based on the type of research study. The quality of evidence was organized into three classes Class I evidence comes from procedures having at least one randomized controlled study to support them. Class II is divided into three subclasses, where II-l involves a well-designed controlled study without randomization. Class II-2 evidence comes from well-designed cohort or case-control studies, preferably carried out at more than one research setting. Class II-3 involves uncontrolled research with dramatic results (e.g., penicillin trials in the 1940s). Class III evidence includes the opinions of experts and authorities in the field based on clinical... 

II-l Well-designed, controlled trials without randomization II-2 Well-designed, cohort or case-control analytic studies, preferably from more than one center or research group... 

Discontinuation trials, either controlled or open, usually are not likely to have any direct benefit and may well have real risks, such as relapse, suicide, and loss of employment. Such studies need additional scrutiny and safeguards to minimize risk and to strengthen consent procedures. There are some situations in which a discontinuation study may be considered. For example, to determine whether long-term treatment is needed, a study design might randomly assign patients who have responded successfully to a particular treatment to either a continuation or discontinuation of that treatment. Relapse rates across these two conditions could... 

Although dexamethasone is commonly associated with transient adverse effects, several randomized trials have shown that it rapidly reduces oxygen requirements and shortens the duration of ventilation. A randomized study was designed to evaluate the effects of... 

Tsukuki RT, Johnson JA, Teo KK, et al. 1999. Study of cardiovascular risk intervention by pharmacists (SCRIP) A randomized trial design of the effect of community pharmacist intervention program on serum cholesterol risk. Ann Pharmacother 33 910. 

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