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M09.01.15 Clinical trials
Clinical trials are experimental studies conducted on human participants to evaluate the efficacy, safety, and potential benefits of medical treatments or interventions. These trials compare therapeutic outcomes between one or more treatment groups and a control or placebo group. The robustness of clinical trial results increases with randomized assignment, controlled conditions, and blinding methods, including:
- Double-blind: Neither participants nor healthcare providers know which group (treatment or control) participants are in.
- Triple-blind: Additionally, researchers analyzing the data are blinded to group assignments, further reducing bias.
Phases of Clinical Trials
Clinical trials are generally conducted in four main phases, each designed to answer a specific question about the treatment’s safety, efficacy, and long-term effects.
| Drug Trial Phase | Typical Study Sample | Purpose |
|---|---|---|
| Phase I | A small number of healthy volunteers or patients | “Is it Safe?” Assesses safety, toxicity, pharmacokinetics, and pharmacodynamics |
| Phase II | Moderate number of patients with disease of interest | “Does it Work?” Examines treatment efficacy, optimal dosing, and adverse effects |
| Phase III | A large number of patients, randomized to treatment or control group | “Is it as good or better?” Compares the new treatment to standard care for efficacy improvement |
| Phase IV | Postmarketing surveillance of approved treatment | “Can it stay?” Detects rare or long-term adverse effects, such as those warranting a black box warning, which could lead to market withdrawal |
Points to Remember
- Randomization: Reduces selection bias by assigning participants to groups randomly.
- Controlled Study: Involves a comparison group (placebo or standard of care) for meaningful assessment.
- Blinding: Minimizes bias by preventing knowledge of group assignments. Increases objectivity, especially in double-blind and triple-blind studies.
- Postmarketing (Phase IV): Essential for monitoring long-term safety and identifying any adverse effects after widespread use.
Types of Clinical Trials
Randomized Controlled Trial (RCT)
An RCT is regarded as the gold standard in epidemiology, where subjects are randomly assigned to either the intervention or control group. This minimizes bias and enhances the study’s reliability.
- Double-Blind RCT: Neither participants nor researchers know which group receives the intervention, reducing bias but increasing study costs.
- Placebos: Often, 25–40% of the placebo group show improvement.
- Standard of Care: Compares current treatments against new interventions.
Community Trials
In a community trial, entire communities or political subdivisions are assigned to receive a preventive or therapeutic treatment. These trials assess how well a treatment works in real-world settings.
Cross-Over Study
A cross-over study allows each group to receive the intervention at different times, addressing ethical concerns of withholding treatment. For example, in an AZT trial:
- Group A: Receives AZT for 3 months, then becomes the control.
- Group B: Starts as the control, then receives AZT in the second 3 months.
Points to Remember
- Clinical trials progress through three FDA-required phases to assess safety, dose, and efficacy.
- Randomized Controlled Trials (RCTs) and Double-Blind RCTs are critical for minimizing bias.
- Community trials focus on community-level intervention effects.
- Cross-over studies are designed to ethically provide treatment to all participants over time.
References
- National Institutes of Health. What Are Clinical Trials and Studies? Retrieved from https://www.nih.gov
- Food and Drug Administration. Clinical Trials and the FDA: Ensuring Safety and Efficacy of New Drugs. Retrieved from https://www.fda.gov
- World Health Organization. Guidelines for Clinical Trials. Retrieved from https://www.who.int