 The story of a medication before it gets to the shelf of a chemist is a long one. Less than 10% of drugs designed by pharmaceutical companies actually end up making it onto the market. That's because most don't pass all the hurdles on the way to being approved for sale. Before a drug even comes near being tested on humans, it's tested on animals. This first step helps scientists test the effects of the drug on vital organs and how toxic the drug is at different doses. Once this hurdle is being cleared, the drug must go through three phases of human trials, known as clinical trials, before it's approved for sale. Phase one is the first time the effects of a new drug are studied in humans. At this stage, it's all about safety. A small sample of up to around 80 healthy volunteers trial the drug to establish its toxicity over a range of doses based on the results of the animal studies. If the drug is found to be safe, it enters the next phase of testing. Phase two of the trial process focuses on the benefits of the drug, whether the drug treats the target condition or minimizes its effects. Several hundred patients with the condition are included in the trial sample, and if there's evidence of a benefit to patients with an acceptable level of side effects, the drug progresses to the third phase. Phase three is the most important phase of drug testing and the last stage before drug developers seek approval from regulatory agencies like the Therapeutic Goods Administration in Australia or the Food and Drug Administration in the US before it goes to market. Phase three is where researchers seek the definitive answers on a drug's efficacy and safety. The number of participants involved and the duration of the studies vary depending on the product and target condition, but hundreds or even thousands of participants are often involved. And the best way of proving a drug's efficacy against the current standard of care is through a randomized control trial. Randomized control trials generally divide study participants randomly into two separate groups. One group of participants receives the new drug while the other is a control group. They receive either no treatment at all, a placebo, which appears to be the treatment, but has no active ingredient, or the standard treatment available at the time of the trial. The two groups are randomly allocated to make sure that effects shown in a trial are the result of the drug itself, rather than factors like age, lifestyle choices, like whether the participants are smokers or live in a specific environment, or gender. And to make sure that effects aren't boosted or hampered by the patient knowing which treatment they're getting, trials are generally what's called blind. Where possible, the researchers and treating doctors are also blinded, so no one knows what treatment a participant is receiving until the results are in. Once the drug clears phase three, it generally gets approved for sale and hits the market. But testing doesn't stop there. That's when phase four kicks in. It's the final safety measure on a drug and focuses on its long-term effects and potential use for treatment in other conditions or new populations, like children. These studies generally involve a wide population receiving the drug, sometimes thousands, and are often a condition of the drug receiving approval. So when you take medication, you can be safe in knowing that it's gone through a process of testing that can take up to a decade.