Page created on January 7, 2022. Not updated since.
How do scientists get ideas for new drugs? In some cases (like opium), they can look to substances that have been used naturally for a long time and use or modify them to suit other needs. However, in most cases, drug development begins by systematically searching for a new molecule that has certain effects. Drug developers can look to already existing drugs and try to modify them to create a new drug with similar, but better effects, or they can try to make molecules that resemble endogenous compounds.
Drugs go through many tests from the time they are first synthesized until they are given to patients. They must be first tested on animals, then tested to see if they are safe for humans, then tested to see if the drug actually has the expected therapeutic effects on humans.
However, these tests are not perfect. It’s impossible to test for all possible side-effects and contraindications, and it’s impossible to know a drugs long-term effect until the drug has been given to patients long-term. The classical example of this is the story of thalidomide.
When a new drug candidate is synthesized, it must first undergo preclinical trials, where the drug is tested on animals for any toxic or unwanted effects. Researches will also use the information collected from preclinical trials to estimate a safe dose to be used in clinical trials.
Then, the drug will begin clinical trials, beginning with phase Ia. Phase Ia clinical trials test the effect of the drug on healthy male volunteers when given in a single dose, to test the acute tolerance of the drug. The reason male volunteers are used is because exposing females to potentially dangerous drugs might negatively affect their eggs. Males produce sperm continuously and therefore don’t have this problem.
Following this, the drug will enter phase Ib where the drug is given in repeated doses, to test the chronic, long-term tolerance.
If the drug passes phase I, it will enter phase II, where there will be pharmacodynamic and pharmacokinetic studies on patients taking the drug over a period of time.
Phase III studies tries to determine the therapeutic effect of the drug in a larger-scale placebo-controlled double-blind study, where half of the patient group is given a placebo drug (a drug that intentionally does nothing, often a sugar pill) and the other half is given the drug in question. Scientists can then compare the results of the two groups to determine the effects of the drug.
If the drug passes phase III trials, it will be commercially available. Later, phase IV studies will be performed, to continue to evaluate the efficacy and safety of the drug.