Table 1.

Phases of clinical trials

	Pharmacological Trials				Medical Device Trials
	Phase I	Phase II	Phase III	Phase IV	Feasibility (preliminary or pilot)	Pivotal
Main goal	Safety	Safety, efficacy	Effectiveness, efficacy, safety	Post-marketing approval, long-term effects	Feasibility and safety	Effectiveness
Design	Open-label	Randomized, controlled, often blinded	Randomized, controlled, typically blinded	Open-label	Open-label and randomized controlled	RCT most common and desirable; possible open-label and non-randomized
Target population	HV and patients	Mostly patients, sometimes HV	Mostly patients	Only patients	Usually patients, possibly HV	Patients
Sample size	Small (n = 20 to 100)	Medium (n = up to several hundred)	Large (n = usually around 300-3000, could be larger)	Large (n = usually more than 1000)	Relatively small (n = usually 10-50)	Larger but smaller than drug phase III (n = usually around 100-300)
Duration	Short	Short (up to 1 year)	Moderate (around 2 years, including follow-ups)	Long (can go up to 3-4 years or an even longer follow-up)	Short (weeks to months)	Usually not as long as drug trials (months)

Abbreviations: HV: healthy volunteers