Opioid dependence and addiction are most appropriately understood as chronic medical disorders, like hypertension, schizophrenia, and diabetes. Opioids are chemically related and interact with opioid receptors on nerve cells in the brain and nervous system to produce pleasurable effects and relieve pain. Opioids are a class of drugs that include the illicit drug heroin as well as the licit prescription pain relievers oxycodone, hydrocodone, codeine, morphine, fentanyl and others. opioid withdrawal is one of the most powerful factors driving opioid dependence and addictive behaviors. Treatment of the patient’s withdrawal symptoms is based on understanding how withdrawal is related to the brain’s adjustment to opioids.
Repeated exposure to escalating dosages of opioids alters the brain so that it functions more or less normally when the drugs are present and abnormally when they are not. Two clinically important results of this alteration are opioid tolerance (the need to take higher and higher dosages of drugs to achieve the same opioid effect) and drug dependence (susceptibility to withdrawal symptoms). Withdrawal symptoms occur only in patients who have developed tolerance. Opioid tolerance occurs because the brain cells that have opioid receptors on them gradually become less responsive to the opioid stimulation. Therefore, more opioid is needed to produce pleasure comparable to that provided in previous drug-taking episodes.
the pleasure derived from opioids’ activation of the brain’s natural reward system promotes continued drug use during the initial stages of opioid addiction. Subsequently, repeated exposure to opioid drugs induces the brain mechanisms of dependence, which leads to daily drug use to avert the unpleasant symptoms of drug withdrawal. Further prolonged use produces more long-lasting changes in the brain that may underlie the compulsive drug-seeking behavior and related adverse consequences that are the hallmarks of addiction.
Symptoms of Opioid Addiction.
For mild to moderate intoxication, individuals may present with drowsiness, pupillary constriction, and slurred speech. For severe overdose, patients may experience respiratory depression, stupor, and coma. A severe overdose may be fatal.
Autonomic symptoms – diarrhea, rhinorrhea, diaphoresis, lacrimation, shivering, nausea, emesis, piloerection
Pain – abdominal cramping, bone pains, and diffuse muscle aching
Central nervous system arousal – sleeplessness, restlessness, tremors
Treatment of Opioid Addiction
The medications most commonly used to treat opioid abuse attach to the brain cells’ mu opioid receptors, like the addictive opioids themselves. Methadone and LAAM stimulate the cells much as the illicit opioids do, but they have different effects because of their different durations of action. Naltrexone and buprenorphine stimulate the cells in ways quite distinct from the addictive opioids. Each medication can play a role in comprehensive treatment for opioid addiction. Despite the effectiveness of medications, they must be used in conjunction with appropriate psychosocial treatments.
Methadone is a long-acting opioid medication. Unlike morphine, heroin, oxycodone, and other addictive opioids that remain in the brain and body for only a short time, methadone has effects that last for days. Methadone causes dependence, but—because of its steadier influence on the mu opioid receptors—it produces minimal tolerance and alleviates craving and compulsive drug use. In addition, methadone therapy tends to normalize many aspects of the hormonal disruptions found in addicted individuals. Methadone treatment reduces relapse rates, facilitates behavioral therapy, and enables patients to concentrate on life tasks such as maintaining relationships and holding jobs. Patients are generally started on a daily dose of 20 mg to 30 mg, with increases of 5 mg to 10 mg until a dose of 60 mg to 100 mg per day is achieved. The higher doses produce full suppression of opioid craving. Patients generally stay on methadone for 6 months to 3 years, some much longer. Relapse is common among patients who discontinue methadone after only 2 years or less, and many patients have benefited from lifelong methadone maintenance.
A longer acting derivative of methadone, LAAM can be given three times per week. Recent concerns about heart rhythm problems have limited LAAM’s use. Dosing with LAAM is highly individualized, and three-times-weekly doses range from 40 mg to 140 mg.
Naltrexone is used to help patients avoid relapse after they have been detoxified from opioid dependence. Naltrexone clings to the mu opioid receptors 100 times more strongly than opioids do, but it does not promote the brain processes that produce feelings of pleasure. An individual who is adequately dosed with naltrex-one does not obtain any pleasure from addictive opioids and is less motivated to use them. Before naltrexone treatment is started, patients must be fully detoxified from all opioids, including methadone and other treatment medications; otherwise, they will be at risk for severe withdrawal. Naltrexone is given at 50 mg per day or up to 200 mg twice weekly. Patients’ liver function should be tested before treatment starts
Buprenorphine’s action on the mu opioid receptors elicits two different therapeutic responses within the brain cells, depending on the dose. At low doses buprenorphine has effects like methadone, but at high doses it behaves like naltrexone, blocking the receptors so strongly that it can precipitate withdrawal in highly dependent patients.