What are the fundamental phases of a clinical trial procedure?

[updated 28 May 2024]


Clinical trials are vital research studies that investigate novel therapies, such as medications, vaccinations, and medical equipment. They are essential in contrasting various therapies to see which ones work best. Clinical trial trials are multi-phase investigations that yield important information on dose, safety, and efficacy. These data help to determine the safety of a medication, its ideal dosage, and its overall effectiveness. Regulatory bodies or ethics committees approve clinical trials, guaranteeing a careful analysis of the advantages and disadvantages. Notably, approval pertains only to the trial and not to the overall efficacy or safety of the medication. Clinical trial results impact judgments about a treatment's broad usage, helping regulatory bodies assess whether it satisfies safety and efficacy requirements for licensure. Clinical trials are essential to expanding our understanding of medicine and guaranteeing the efficacious and safe use of novel medicines for patients.


There are three primary phases of clinical trials in research: phases 1 through 3. Phase 1 trials correspond to the first stages, and phase 3 trials represent the later stages. Furthermore, phase 4 trials take place after licensure, and some trials incorporate an earlier stage known as phase 0.

Let's talk more about the stages that make up a clinical trial.



To ensure the least amount of harmful effects, healthy participants are given a 1/100th dose in the first phase. This phase, which involves 10–15 individuals, focuses on drug absorption, distribution, metabolism, and excretion (ADME) and lays the groundwork for future research.


In a phase 1 clinical trial, a small sample of healthy individuals (typically 20 to 80) are studied to determine how a medication affects them. The participants do not have any underlying medical issues. This stage's objective is to ascertain the maximum dosage of the drug that can be administered without having a significant negative impact. During this phase, participants are closely observed to see how their bodies respond to the medicine. Preclinical research offers some guidance on dosage, but the effects of a drug on the human body are not always predictable. Apart from assessing safety and determining the optimal dosage, researchers also consider the most effective method of medication administration, including topical, intravenous, and oral routes.

Approximately 70% of medications get to the next stage, according to the FDA.


Researchers examine a drug's effects on several hundred individuals who have the ailment that the new drug is intended to treat during a phase 2 clinical trial. Usually, the same dosage that was determined to be safe in the preceding phase is administered to them. For several months or years, participants are observed by researchers to assess the medication's effectiveness and provide additional data regarding potential negative effects. Even while phase 2 includes a larger participant pool than previous phases, it is still insufficient to show a medication's general safety. But the information gathered in this stage aids researchers in devising procedures for phase 3.

Approximately 33% of medications get to the next stage, according to the FDA.


Researchers examine the efficacy of a novel drug in comparison to currently available treatments for the same ailment during the phase 3 clinical study. They have to show that the new drug is at least as safe and effective as the available ones in order to move further. In order to do this, the researchers use randomization, allocating to some volunteers at random the new medication and to others the one that already exists. Phase 3 trials are usually double-blind, meaning that bias is minimized because neither the subjects nor the researchers know which medicine is given. A phase 3 clinical trial is usually required by the FDA before authorizing a new drug. This phase is more likely to reveal unusual and long-term negative effects because to the bigger participant pool and longer duration. Between 25 and 30 percent of drugs move on to the next stage.


Clinical studies in phase 4 are carried out following FDA approval of a medication or technology. This phase's goals are to monitor the drug's effectiveness in real-world settings, evaluate its long-term risks and benefits, and spot any unusual adverse effects. Over several years, thousands of people participate in this phase. Phase 4 research is used by investigators to obtain more data about the long-term safety, efficacy, and possible advantages of the treatment.

It is clear from examining the phases of clinical trials that each one is critical in forming our knowledge of the safety, effectiveness, and practical implications of a novel medicine. These trials move us closer to creative and practical medical solutions because they are guided by thorough research and ethical concerns.

















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