With all the testing they do on medicines, why does it take years to find out that some are addictive?

Question

They've already used it on guinea pigs (human or whatever) before it's approved by the FDA...couldn't they see how those reacted to the medications...........

Answer 1

Well you have to do very specific tests on animals to test for addictive properties so often drugs wont be tested for this. Also addiction is only beginning to become understood in the scientific world - therefore its hard to predict what will and wont be addictive. And one more point - many drugs work, but often the case is that its not known WHY they work. Ending up with many side effects such as addictive properties. Oh and another point - some drugs are so effective at something else, that often the risk of addiction is better then letting something go untreated eg with morphine being used as a analgesic.

Answer 2

When they develop and test drugs, it is in a strict lab setting where many factors can be controlled. The difficulty with clinical testing is that no one can really predict with certainty the long term effects of the drug's continuous use. This is the reason why some drugs can only be obtained with a prescription and why doctors closely monitor the response of the patient.  

Although factors such as age, body weight, and prior medical history are considered by doctors when they prescribe medications, individuals respond to medicines differently. The medicine will only be banned due to its addictive properties if too many patients become overly dependent on the drug, and it can take years before this pattern becomes apparent.