Welcome. The theme of this lecture is the opioid epidemic. What is the opioid epidemic? It is the rapid increase in addicted individuals and deaths due to the use of opioid or morphine related drugs that has occurred over the past 20 years or so. More than 64,000 drug overdose deaths occurred in 2016. In addition to the deaths, there's the problem of addiction and its human costs. Note that the word opioid means the same as the word opiate used earlier in this course. Where do the drugs come from? How do we get them? Nearly a quarter of a billion prescriptions were written for opioid drugs in 2013, and almost half of the opioid deaths that occur involve prescription drugs. Excessive availability, through prescriptions are part of the problem. Also, the illegal selling of opioid drugs by criminals are also a major part of the problem. Does society need opioid drugs? Well, yes. Opioids are the drugs used for treating moderate to severe pain and are, in fact, the only widely accepted drugs for treating this. No non-addicting alternative is widely accepted. It is unfortunate that, in higher doses, these drugs can lead to a fatal overdose, and they are, therefore, life-threatening. As you already know from earlier in this course, individuals like to take opioid drugs, not only because they're painkillers but also because they produce euphoria or pleasurable feelings. The drugs are sometimes taken by people who have no pain at all but who want the pleasurable feelings. When we use the term opioid, we refer to many different kinds of drugs. There are illegal compounds such as heroin and prescription drugs such as oxycodone and morphine. What are the physiological effects of opioids? Well, the effects of opioid drugs that we are addressing here include pain relief and euphoria. But they also cause a depression of breathing, drowsiness, and sedation and yet other effects. The intensity of the effects depend on the dose of the drug taken. More euphoria requires more drug, but this also produces a greater suppression of breathing. The desire to experience a greater high motivates users to take greater amounts of drug, which could lead to an unintended fatal overdose due to a depression of breathing. There are various properties of opioid drugs that contribute to this problem. One property is that the drugs differ in potency. Some of these drugs are more potent than others. More potent drugs produce their effects at lower doses, for example, fentanyl is 30 times more potent than morphine and will produce pleasurable feelings at only one-thirtieth of the dose of morphine. If one has been using morphine and has become accustomed to taking a certain quantity of morphine, a sudden switch to the same quantity of fentanyl could easily result in an unintended overdose and death. Additional properties include, with repeated drug-taking, tolerance and dependence. Tolerance, as described earlier, is the state where, over time, more drug is needed to produce the same effect or where the same dose of drug gradually loses its effectiveness. More drug is needed to produce the same high than when the drug was first taken. This escalation in dosing is a factor in causing overdose. Drug dependence means that when the drug is not taken, withdrawal symptoms begin to occur. In general, they are the opposite of the acute effects described earlier. Withdrawal is terminated or alleviated by taking more opioid drug. Avoidance of and alleviation of withdrawal, sometimes in a desperate state of mind, seems to be another factor in causing overdose. Finally, the property of addiction keeps the addict involved with these dangerous drugs. Why do drugs have any effect at all? How did they work? The answer is that endogenous or naturally occurring opioid systems are normally found in the brain. They're the basis for opioid drug action. As noted earlier in this course, various drugs are able to produce effects such as euphoria and addiction because the brain is already set up for them. The brain already has receptors and nerve cells that use endogenous opioids as neurotransmitters. The nerve cells that use endogenous opioids as neurotransmitters are widely distributed throughout the brain and the body. The endogenous opioid neurotransmitters are not molecules like heroin or fentanyl, rather they are peptide neurotransmitters. Peptides are strings of linked amino acids. The same receptors for these opioid peptide neurotransmitters are used by the opioid drugs, such as morphine. There are several different receptors for the various opioid peptides. One of these, referred to as the mu receptor, is the one mostly associated with pain relief, addiction and euphoria and it also causes respiratory depression. These effects are all linked at a fundamental receptor level. In summary, opioid drug use has escalated over the past years, resulting in numerous overdose fatalities. The drugs come from excessive prescriptions and from criminal sources as well. Note that the term opioid is just another name for opiate. We cannot abandon the use of these drugs because they are the best medicines for treating moderate to severe pain. Certain properties of these drugs, such as variation in potency, depression of breathing, tolerance, withdrawal and addiction, make them more likely to cause a fatal overdose. The basis of the actions of opioid drugs is the existing and naturally occurring opioid peptide system in the brain.
