Table 2. Clinical trial designs, their advantages, and disadvantages.

This table has been created by the authors.

Trial design type	Type of the study	Nature of study	Advantages/disadvantages
Parallel	Randomized	This is the most frequent design wherein each arm of the study group is allocated a particular treatment (placebo (an inert substance)/therapeutic drug)	The placebo arm does not receive the trial drug, so may not get the benefit of it
Crossover	Randomized	The patient in this trial gets each drug and the patients serve as a control themselves	Avoids participant bias in treatment and requires a small sample size. This design is not suitable for research on acute diseases.
Factorial	Non-randomized	Two or more interventions on the participants and the study can provide information on the interactions between the drugs	The study design is complex
Randomized withdrawal approach	Randomized	This study evaluates the time/duration of the drug therapy	The study uses a placebo to understand the efficacy of a drug in treating the disease
Matched pairs	Post-approval study	Recruit patients with the same characteristics	Less variability