Final answer:
The three clinical trial phases for human studies include Phase 1 for safety and pharmacokinetics, Phase 2 for dosage efficacy, and Phase 3 for comprehensive efficacy and safety testing in a large population.
Step-by-step explanation:
The three phases of clinical study on humans are: Phase 1, Phase 2, and Phase 3. Phase 1 trials focus on the safety and tolerability of a drug, along with its pharmacokinetic properties like absorption and elimination. During Phase 2 clinical trials, researchers evaluate the effective dose needed for the intended therapeutic effect, and Phase 3 involves extensive testing with a large patient population to establish the drug's efficacy and safety profile. Once a drug has successfully passed through these three phases, it may receive FDA approval. Additionally, there is a Phase 4, which takes place post-approval for continuous safety monitoring and to satisfy any additional FDA requirements.