Late last week, the esteemed Drugmonkey pointed me toward an article that came out in the Washington Examiner. The Drug Czar of the Bush administration expressed shock and outrage when he suddenly found out that drug researchers give addictive drugs to human addicts as part of studies on human addiction. Shock me, shock me, shock me, with that deviant behavior. I think Drugmonkey expressed it best when he said
It is harmful to our Nation’s public policy on drug control and substance abuse to run roughshod over the scientific information in this way. It is specifically harmful to drug abuse science to misrepresent the studies in this way.
No kidding. But, issues of politics aside, there are ethics issues associated with giving drug addicts drugs. Janet has done an excellent job (as usual) of explaining the ethical implications of giving drugs to drug addicts. But there’s a third topic that needs to be addressed. We do lots of animal studies with addictive drugs, why do we need to be giving it to humans?
Well, the fact is that rats can’t tell us everything. People who use animals self-administering addictive drugs can learn a lot of things. They can find out how often animals self-administer the drug in specific doses, which can help us to figure out how long the subjective effects of a drug last. We can know the biochemical half-life of a drug without knowing what that means to the animal, and self-administration can teach us which drugs you feel only for 15 minutes (like cocaine), and which you feel for hours (like MDMA), before you have to take another hit.
Self-administration studies can also show which drugs are preferable, by giving an animal a choice and seeing which one they go for. This is different from drug self-administration in humans, when the drug of choice is often a matter of price or availability, and may not actually be the more rewarding or reinforcing choice. Researchers can also use this drug discrimination ability to see how new drugs may act neurochemically, by asking the animal which drug it feels closest to.
Drug research in animals can tell us a LOT about the neurochemical activity of drugs, how they act, where they act, and what acute and chronic effects in the brain look like. These are effects we often can’t see in humans.
Finally, animal research studies can show which drugs are more likely to be addictive, based on whether an animal will self-administer it. Animals will rapidly and reliably self-administer cocaine, morphine, or heroin. Alcohol is more difficult, as it tastes bad, and most rodents don’t have a gag reflex. Drugs like LSD are almost never self-administered, which can tell you a lot about the addictive potential.
But animal studies simply can’t tell you everything there is to know about drug abuse and addiction. First of all, drug dependence is a disease that is characterized primarily by its symptoms, not by a cause. We know you are addicted to drugs because you crave them, can’t quit them, feel withdrawal when you’re not on them, etc. But there’s nothing we can really look for in your body as an underlying cause of addiction. No virus, very little in the way of particular genetic codes.
And the fact is, drug dependence in society depends on far more factors than you could ever simulate in a lab animal. People with drug dependence often have comorbid psychiatric disorders, which themselves are extremely difficult to model in an animal. People are often dependent on more than one drug, or abusing more than one drug, and no person’s drug cocktail of choice, or their drug history, is exactly the same. While we use animal models to figure out the specific effects of certain drugs, effects are sometimes different when we look in humans with variable drug histories.
Additionally, while we may be able to figure out a drug that might help drug addiction by testing in the laboratory, we need to to know HOW it’s stopping drug intake. An animal will stop intake when exposed to certain drugs, but it can’t tell you why. We need to perform studies in humans to find out whether their craving is decreased, their withdrawal symptoms are decreased, or whether they just don’t feel very good. Animal studies can only tell us these things in a very limited way.
Not only that, WHY people start taking addictive drugs is something that is very hard to model in the lab. Some people may take addictive drugs due to stress, which is something we can model, but other are self-medicating for underlying conditions. Each person’s underlying condition is different, and not all of them can be modeled well in animals. While a drug might help to reduce drug administration in laboratory animals, it needs to be tested on humans to determine whether it will work with a given person’s underlying conditions. And it needs to be tested on humans in the presence of drug, to look for potential interactions.
Rats certainly can tell us a lot about cue-induced drug responding, changes in the brain in response to chronic drugs, etc. But only a human can tell us what a drug really FEELS like. Only a human can tell us WHY they are taking what they are taking. Only a human can describe the feeling that goes along with tolerance, and only a human can tell us how other drugs compare in terms of how good or bad they feel. The bottom line is, only a human can talk. Until we can get a rat that can tell us about his bad day at work and how he just wanted ONE drink, we will have to be doing at least some drug addiction research on humans.
