Parallel-group designs

The advantages of a parallel-group design can be summarised as follows ... 

Choosing the most appropriate design (for example using a cross-over design rather than a parallel group design where this is appropriate)... 

The simplest trial design of course is the parallel group design assigning patients to receive either treatment A or treatment B. While this is a valid and effective design... 

Consumption by postmenopausal women (6-month parallel-group design) of soy protein (40g/day providing either 56 mg isoflavones/day or 90 mg isoflavones/day) compared to cesin and nonfat dry milk (40g/day) produced significant increases in bone mineral content and density in the lumbar spine (but not in any other parts of the body), but only in the higher isoflavone (90 mg/day) group compared to the control group.Daily intake for 2 years of... 

In contrast to the parallel group design, in which a given individual receives only one of the two treatments, subjects in a cross-over trial receive both treatments... 

Focus on the Parallel Group Design in This Book... 

Open label study with three treatment groups, with multiple oral doses of 25 mg (Treatment Group I) and 50 mg (Treatment Group II) once daily, immediately after intake of a standard breakfast in a parallel-group design. Safety information and bioanalytical data were reviewed to determine the dose for Treatment Group III (multiple oral doses of 75 or 100 mg XYZ1234). 

The simplest and probably most frequently used design for a clinical trial is the parallel-group design. Eligible patients are randomly assigned to receive one and only one of several treatments or treatment regimens. 

Only two major design types will be dealt with here, cross-over and parallel groups designs, also called paired and un-paired designs. 

The fundamental assumption in bioequivalence assessment is that systemic clearance of the drug remains constant across phases of the study (crossover design) or between the animals used in the study (parallel-groups design). This follows from the equation... 

Generally, crossover studies are more complicated than parallel-group designs. Patients are exposed to more than one test medication, in sequential treatment periods, perhaps with periods of no therapy intervening between those of active therapy. Active therapies may be different drugs, or different doses of the same drug, or, in complicated studies, both. 

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