Opioids

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Opioids: 

Opioids Addiction and Treatments Shariq Chudhri Medicinal Chemistry Dr. John Buynak

Opioid Addiction and Treatments- Overview: 

Opioid Addiction and Treatments- Overview What are Opioids? Addiction and Dependence Mechanism of Dependence Tolerance Treating Addiction Cold Turkey Approach Traditional Drug Treatment Rapid Detoxification Conclusions and Future Avenues For Research

What are Opioids? (A quick review!): 

What are Opioids? (A quick review!) Opioids are a class of drugs that act primarily on the body’s opioid receptors. Opioids are often referred to as narcotics. They act by blocking μ, κ, σ and possibly δ receptor classes. Most opioid receptors are found in the central nervous system and in the gastrointestinal tract. Opioids are used primarily for their analgesic effects but also for their cough suppressant properties. Morphine

Blocking of the Opioid G Receptor (Opioid Agonists): 

Blocking of the Opioid G Receptor (Opioid Agonists)

Addiction and Dependence: 

Addiction and Dependence Drug addiction is a condition in which an individual has lost the power of self-control with reference to a drug and abuses the drug to such an extent that the individual, society, or both are harmed. Dependence refers to a state resulting from habitual use of a drug, where negative physical withdrawal symptoms result from abrupt discontinuation. The key is that addiction results when the reward pathways in the brain are stimulated by drug use thereby causing dependence due at least in part to psychological reasons. Dependence implies need of the drug to avoid withdrawal symptoms, not to gain a reward response in all cases. Palliative care patients do not experience a “high” when taking an opioid and are therefore not considered to be addicted.

Mechanism of Dependence and Addiction: 

Mechanism of Dependence and Addiction Dependence occurs when, after a constant supply of the opiate, the brain shows adaptation, or changes in its circuitry. When that drug is taken away, neurons that have been inhibited start pumping out neurotransmitters again. This imbalance of chemicals in the brain interacts with the nervous system to produce the classic opiate withdrawal symptoms: nausea, muscle spasms, cramps, anxiety, fever, diarrhea.

Tolerance: 

Tolerance Tolerance, describes the need for a drug user to administer larger and larger doses of the drug to achieve the same psychoactive effect. When the body's chemical equilibrium is upset, as in habitual drug-taking, the body sets up oppositional processes to restore itself. More of the drug is needed to overcome these efficient corrective processes. While considerable debate exists about the mechanisms of opioid tolerance, two factors have been isolated with a degree of certainty. Receptor Downregulation- Opioid receptors in the body are actively reduced due to overexposure to opioids. This can also have an effect on endogenous opioid peptide function (i.e. regular functioning of endorphins) Antiopiates- Chemicals like neuropeptide FF, orphanin FQ/nociceptin, and Tyr-W-MIF-1 have all been found to block the function of opioids. This activity is due to the fact that these drugs can block g-protein activity.

Treatments: 

Treatments Several treatments and treatment strategies exist for opioid addiction. The Cold Turkey Approach Traditional Opioid Drug Treatment Rapid Detoxification

The Cold Turkey Method: 

The Cold Turkey Method Quitting opioid use cold turkey after dependence has developed has several drawbacks but also some advantages. Of course, this is the cheapest method of ending dependence. This body, however, is put through a significant amount of stress during the “withdrawal” period. Death or seizures almost never result from opioid withdrawal unless the amount of opioid being withdrawn was extremely large. These events are more likely to occur during withdrawal from barbiturates or benzodiazepines.

The Cold Turkey Method- Withdrawal Symptoms: 

The Cold Turkey Method- Withdrawal Symptoms About eight to twelve hours after the last heroin use, an addict's eyes begin to tear and he/she starts to experience flu-like symptoms: sneezing, weakness, depression, muscle cramps, nausea, vomiting, diarrhea. The symptoms increase in severity over two to three days. Within a week to 10 days the illness is over. The phrase 'cold turkey' probably comes from the appearance of goose bumps all over the body, which resembles a plucked turkey. Muscle spasms in the legs produce kicking movements, and this may be the derivation of the expression 'kick the habit.'

Traditional Drug Based Treatments: 

Traditional Drug Based Treatments The primary method of treating and managing opioid addiction and dependence has been with the use of other opioid drugs. These replacement drugs function to essentially wean the user off of opioid use. Most of these drugs have withdrawal symptoms lighter than those of the abused opioid (heroin, Oxycontin, morphine, etc…)

Traditional Drug Based Treatments- Methadone: 

Traditional Drug Based Treatments- Methadone A synthetic opioid, used medically as an analgesic and in the treatment of narcotic addiction. Although chemically unlike morphine or heroin, methadone also acts on the opioid receptors and thus produces many of the same effects. Chemically, methadone is the simplest of the opioids. Methadone has a slow metabolism and very high lipid solubility, making it longer lasting than morphine-based drugs. Methadone has a typical half-life of 15 to 60 hours, in rare cases up to 190 hours. permitting the administration only once a day in heroin detoxification and maintenance programs. Methadone has traditionally been provided to the addiction population in a highly regulated methadone clinic, generally associated with an outpatient department of a hospital. Numerous clinics start addicts at 30mg and raise the dosage 10mg a day until the addict feels they are at a comfortable level of dosage.

Traditional Drug Based Treatments- Methadone, continued…: 

Traditional Drug Based Treatments- Methadone, continued… At proper dosing, methadone usually reduces the appetite for and need to take heroin. However, most heroin addicts report more difficulty in quitting methadone than heroin. While there is much debate over the treatment schedule and duration required, treatment at a methadone maintenance clinic is intended to be for an indefinite duration. Many factors determine the treatment dose schedule, and some follow the philosophy that methadone maintenance treatment is not curative for heroin addiction.

Traditional Drug Based Treatments- Methadone- History: 

Traditional Drug Based Treatments- Methadone- History Methadone/dolophine, was first synthesized in 1937 by German scientists Max Bockmühl and Gustav Ehrhart at IG Farben during their search for an analgesic that would be easier to use during surgery (and less potentially addictive, post-op) than morphine…) Methadone was introduced into the United States in 1947 by Eli Lilly and Company as an analgesic. A great deal of anecdotal evidence was available "on the street" that methadone might prove effective in treating heroin withdrawal and it had even been used in some hospitals. It was not until studies performed at the Rockefeller University in New York City by Professor Vincent Dole, along with Marie Nyswander and Mary Jeanne Kreek, that methadone was systematically studied as a potential substitution therapy. To date, methadone maintenance therapy has been the most systematically studied and most successful, and most politically polarizing, of any pharmacotherapy for the treatment of drug addiction patients.

Traditional Drug Based Treatments- Buprenorphine: 

Traditional Drug Based Treatments- Buprenorphine an opioid drug with partial agonist and antagonist actions. In October 2002, the FDA additionally approved Suboxone and Subutex, buprenorphine's high-dose sublingual pill preparations for opioid addiction. Belongs in the Schedule III category of drugs along with hydrocodone and anabolic steroids. Advantages to using buprenorphine over methadone include less restrictive availability. A patient can be prescribed the drug for self administration rather than having to receive their dose at a clinic. Also, it is thought that Buprenorphine has less severe withdrawal symptoms than methadone although the symptoms may last longer.

Traditional Drug Based Treatments- Naltrexone: 

Traditional Drug Based Treatments- Naltrexone Naltrexone is an opioid receptor antagonist used primarily in the management of alcohol dependence and opioid dependence. Naltrexone, and its active metabolite 6-β-naltrexol, are competitive antagonists at μ- and κ-opioid receptors, and to a lesser extent at δ-opioid receptors. The plasma half-life of Naltrexone is about 4 h, for 6-β-naltrexol 13 h. The blockade of opioid receptors is the basis behind its action in the management of opioid dependence—it reversibly blocks or attenuates the effects of opioids. Because the drug is merely a receptor antagonist, it blocks the effects of opioids but does not reduce the craving for opioids. As such, Naltrexone is found to be effective mostly for treatment of people in stable social situations such as addicted health care professionals. Even so, compliance with treatments is a continuing problem for which implantable Naltrexone release devices are being increasingly used.

Rapid Detoxification: 

Rapid Detoxification A technique that aims to reduce the duration and intensity of opioid withdrawal by administering a combination of drugs while the patient is under general anesthesia. The process involves intubation and external ventilation of the patient coupled with the administration of opioid receptor antagonists (blockers). The most often used drugs are Naloxone and Naltrexone. Naloxone is a powerful Mu opioid receptor antagonist that is capable of rapidly displacing other opioids from the opioid receptors. As a result, massive withdrawal symptoms are triggered but are attenuated by the fact that the patient is under anesthesia. As with Naltrexone treatment alone, the Rapid Detoxification procedure cannot reduce the craving aspect of addiction and traditional drug based follow up treatments are necessary to manage the addiction although dependence has ended.

Patient undergoing Rapid Detox: 

Patient undergoing Rapid Detox

Conclusions: 

Conclusions Opioid addictions is a serious issue that must be given more thought than at present in the scientific community as well as in politics. Current treatments are only partially successful in breaking the hold of addiction and dependence on the addict. Research can and must be done into other treatments and drugs that are more effective in not only reducing physical dependence and withdrawal symptoms but also in blocking addict’s tendency to continue to crave the drug.

References: 

References http://opioids.com/tolerance/molecular.html http://en.wikipedia.org/wiki/Opioid http://pharmrev.aspetjournals.org/cgi/content/abstract/2/2/355 http://en.wikipedia.org/wiki/Morphine http://en.wikipedia.org/wiki/Pethidine http://www.drug-addiction.com/opioids.htm http://opioids.com/tolerance/index.html- Opiate tolerance and dependence: receptors, G-proteins, and antiopiates by Harrison LM, Kastin AJ, Zadina JE Tulane University School of Medicine and Veterans Affairs Medical Center, New Orleans, LA 70112-1262, USA. Peptides 1998; 19(9):1603-30 http://www.emedicine.com/emerg/topic643.htm http://en.wikipedia.org/wiki/Methadone http://en.wikipedia.org/wiki/Naltrexone