Study Arms

A study arm of a clinical trial includes the active arm, which is the test product, a possible reference arm, which could be another active approved product, and a placebo arm. Additional arms of the study can include other approved reference products or additional doses of the drug product.

Study arms can be implemented in a parallel design, whereas two or more drugs are randomly assigned to different patients or a crossover design where the patient takes each treatment in a random fashion.

It is important to determine the appropriate number of study arms in your clinical trial because the outcome of your clinical trial may depend on this. In order to present reliable data to the agency, well-designed studies are important. Statistical plans depend on the number of study arms employed in your study.

In addition, the number of subjects in each arm is important. It is feasible to make the active groups larger than the placebo groups to improve the precision of the active drug comparison.

Combination or factorial design studies can be employed to add several dosing arms in combination with several doses of approved agents in combination. This is common in antihypertensive therapies where combination therapy is a standard of care.

In addition, study arms could also have a placebo group for each drug, a double-dummy placebo-controlled trial design. When comparing the efficacy and safety of two products that have different routes of administration, a double-blind double-dummy study design can be used. A placebo can be given for each route, along with its corresponding active treatment to maintain the integrity of the blinding.