For many people, controlled drug trials are an easy way to make a little extra money with little to no effort needed on your part, but it may be of use to note the potential risks involved. Before we discuss the safety of participating, it's advantageous to fully understand exactly what a clinical trial entails.
By definition, a clinical trial is the controlled testing of a new medicinal compound, which takes note of the safety and efficacy of its use in the wider public. Without these, there would be no way to tell if a chemical is going to be a useful cure, or a dangerous medicine which could cause a lot of harm to unsuspecting imbibers.
It's very important to realise that when you take part in a drug trial, it has already undergone rigorous standards checking. To be able to legally induct participants, the Research Ethics Committee must first decide whether the agreed test is ethical for the proposed research. Their job is to ensure the safety of all trialists, and are responsible for the decision making process that takes place when deciding on the methodology and efficacy of the trial.
After that, the proposal is passed on to the MHRA (Medicines and Healthcare Products Regulatory Agency), who will check that the medicines involves are of a standard that will not endanger any of the active parties. If a drug has an unusually high risk of causing damage, it will be scrapped at this stage and won't make it out of the research laboratory.
With this in mind, it's clear that your safety is of the utmost importance to all of the responsible bodies. The lengthy process of legal, ethical, and risk testing is in place to ensure that: not only will the results be helpful to the doctors involved, but also that any potential exposure to hazardous chemicals are absolutely minimised.
Through precise criterion in the testing phase and highly skilled research scientists, they have perfected a method of providing willing contributors with a way to advance medical science, and massively decreased the risk of harm. In today's world, it is absolutely safe (and recommended) to participate in drug trials.
You can find more information about participating in medical trials at Parexel.