Placebo-controlled, parallel group design

As noted earlier, in the only double-blind, placebo-controlled, parallel design study of clonidine, Janicak et al. ( 264) studied a group of acutely ill, hospitalized manic patients, many with associated psychotic features. After a washout period averaging 1 week, patients were randomly assigned to receive either clonidine or placebo for a 2-week trial. The intent was to ascertain whether clonidine alone had any inherent antimanic properties, and therefore, no other concomitant psychotropics were allowed. Unfortunately, improvement in either group was minimal and did not differ, with some patients on clonidine developing problems with rash and hypotension. Doses of clonidine were comparable with those reported in prior positive studies, averaging 0.5 mg/day. 

One solitary controlled trial is on record, comparing CBD (200-300 mg daily for up to 4.5 months added to standard therapy) with placebo in a double-blind, parallel-group design in 15 poorly controlled patients with secondary generalised epilepsy (Cunha et al. 1980). Half the CBD patients remained almost free of fits throughout the experiment and all but one of the others showed partial improvement . With a single exception, the placebo patients remained unchanged. Drowsiness in a quarter of the patients was the only unwanted effect associated with CBD. 

Singh and coworkers (1998) reported a randomized, double blind placebo-controlled, fixed-dose study of kava (Kavatrol ) within a parallel groups design. Sixty... 

The better-designed studies included double blind, placebo-control conditions within a parallel research design. However, most studies did not provide any data on how they randomized or counter-balanced their experimental and placebo or control groups. No studies explicated how they were able to match the two groups in terms of the severity or duration of the subjects anxiety states. Future studies should use a more robust research methodology, such as a double blind, placebo-controlled, cross over design. 

The TQT study is a randomized, placebo- and positive-controlled clinical trial that can adopt a crossover design or a parallel-group design. The traditional four treatment arms are as follows ... 

The parallel-group, double-blind, placebo-controlled study design represents the golden standard of acute treatment trials of depression, mania and anxiety disorders. This design is intended to limit bias, in particular selection and measurement bias. Trials based on this design are expected to provide information about the effect size of a new compound and its side-effect profile. 

The Alzheimer s Disease Anti-inflammatory Prevention Trial (ADAPT) was another well designed quality chnical study that point toward increase risk of cardiovascular disease associated with the long term use of naproxen compared to placebo group. [153] ADAPT was a randomized, parallel, placebo-control-led, multicenter trial intended to study the efficacy of a naproxen (220 mg po twice a day) and celecoxib (200 mg po twice a day) vs. placebo. A total of 2, 625 dementia-free patients over age of 70 years were enrolled.. These data showed an apparent increase in cardiovascular and cerebrovascular events among... 

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