JL: What is the difference between physical dependence, tolerance, and addiction?
Dr. Schneider: There’s a huge difference. Physical dependence is a property of many different classes of drugs, not just drugs that can be abused. Physical dependence is a property of steroids, for example. What it means is that if a person stops that drug suddenly, there is a predictable physiologic response by the body.
For example, when you are physically dependent on exogenous steroids, meaning steroids that are outside the body in medication form like prednisone, your brain stops putting out chemicals that cause your body to release endogenous steroids, the steroids produced within your body. The pituitary gland normally puts out a hormone that stimulates the adrenal gland to produce epinephrine, which is adrenalin. When you’re on the steroid medication, the body stops producing it. What happens is, if you stop taking prednisone suddenly, your body is left without the endogenous steroids, the steroids your body usually produces. Clearly, the person has become physically dependent on the prescribed steroids and the solution to it, if they don’t need the medication any more is to taper it slowly so that the body gets a chance to reverse those changes. Opioids also can, and usually do, cause physical dependence. The body makes changes to adapt to the opioids and if you stop suddenly, you get this unpleasant withdrawal syndrome.
That’s what physical dependence is — it has nothing to do with addiction. Addiction is not necessarily a physical thing. Addiction is a psychological phenomenon consisting of three elements. One is loss of control, which means you intend to use only so much but when you have access you keep taking the substance. The second is continuation despite significant adverse consequences, which means even if the substance – let’s say alcohol -- is causing liver damage, you’re arrested for a DUI, or are fired from your job, you still take it. In fact, one of the major differences between chronic pain patients and addicts is that the opioids expand the life of the pain patient. They make things better — they improve the patient’s functioning and pain whereas with the addict, their life constricts and they become more and more focused on the drug that they are misusing. So you have the opposite effect, and that’s what I’m talking about when I say addicts continue to use it despite adverse consequences. Pain patients on prescribed opioids don’t have adverse consequences — they may have side effects from opioids but they don’t have these types of adverse consequences (eg, loss of a job, organ damage). The third element of addiction is the preoccupation or obsession with obtaining, using, and recovering from the effects of the drug.
Tolerance is the need for more to get the same effect. Tolerance is a big issue in prescribing opioids. Everyone knows that drug addicts have to keep increasing their dose to get a high. What most people don’t know is that tolerance to the different effects of opioids differs What I’m saying is there are generally four effects of opioids on the body. Three of them we call side effects and these are sedation, nausea and constipation. The fourth effect is the desired one -- pain relief. So opioids have four effects. It turns out that tolerance, meaning that you get less effect as you continue the same dose or that you need more medication to get the same effect, tolerance develops to two out of those four effects — sedation and nausea. Doctors realize you don’t develop much tolerance to constipation and that patients taking opioids have to be on a bowel program. But, what most doctors and patients do not realize is that you don’t develop much tolerance to the pain-relieving effects of opioids. What happens — when it comes to pain relief — is that most patients, once they’ve reached an effective dose, stay on the same dose for a long time. Sometimes they need a little upward increase but it’s not a significant thing. The usual reasons that a chronic pain patient needs a dose increase is either that they’re doing more physical activities, or that their disease has progressed.
So why is it that heroin addicts need more and more? The reason is because tolerance develops very, very quickly to the euphoria-producing effects of the drug. What causes a buzz from a drug is not the concentration in the blood stream. For example, you can have pain patients who have a little bit of the drug in their body and other pain patients who have a very high level in their blood in order to get pain relief, but neither of these people are likely to experience a buzz. What causes a buzz is the rate of increase — rate of change — in the brain. People develop a tolerance very rapidly to this. So anytime somebody says, “Isn’t true that people become tolerant to opioids?” the answer has got to be, “What do you mean by tolerance? What specific effect of the opioids are you asking about?” That’s a really important point. You don’t just develop tolerance or not develop tolerance. It’s a widespread misunderstanding.