Opioid Addiction

Article Author:
Martin Huecker
Article Author (Archived):
Mohammadreza Azadfard
Article Editor:
James Leaming
Updated:
2/28/2019 3:57:47 PM
PubMed Link:
Opioid Addiction

Introduction

Opioid use disorder and opioid addiction are reaching epidemic levels in the US and worldwide. Three million US citizens and 16 million citizens worldwide have had or currently suffer from opioid use disorder. More than 500,000 in the United States are dependent on heroin. Eleven criteria define opioid use disorder.

The diagnosis is made by meeting two or more criteria in a year time period. Key elements are as follows:

  • Increasing dose/tolerance
  • Wish to cut down on use
  • Excessive time spent to obtain or use the medication
  • Strong desire to use
  • Use interferes with obligations
  • Continued use despite life disruption
  • Use of opioid in physically hazardous situations
  • Reduction or elimination of important activities due to use
  • Continued use despite physical or psychological problems
  • Need for increased doses of the drug
  • Withdrawal when dose is decreased

The drastic increase in opioid use disorder is at least partially due to overprescribing of opioid medications. In particular, the 1990s saw an explosion in opioid prescribing due to the pain as fifth vital sign campaign, downplay of the abuse potential of opioids, and aggressive marketing of drugs such as oxycontin and Opana.

Etiology

The prevalence of opioid addiction globally results from many factors. In the 1990s, in the United States, increasing prescription of opioid pain medications contributed significantly to addiction. These prescription drugs were misused, and many individuals became dependent. It was common to prescribe opioid medications for mild to moderate acute pain, and these medications were often continued indefinitely. Physicians prescribed the drugs with no intention of tapering or ceasing use.

Due to pharmacologic effects, opioids are highly addictive. Tolerance is achieved within days, and the withdrawal syndrome is severe.

Epidemiology

Opioid addiction afflicts individuals from all socioeconomic and educational backgrounds. Four million people admit to the nonmedical use of prescription opioids. Perhaps more concerning, 400,000 people had used heroin in the past month based on data from 2015 through 2016. Roughly 80% of new heroin users in the United States report their initial opioid was a prescription pill.

From 2002 through 2011, approximately 25 million people in the United States began nonmedical use of pain relievers. According to survey data, in 2015, 91.8 million individuals in the United States alone used prescription opioids. More than 11 million misused the medications.

Emergency department visits due to complications and overdose have increased annually since 2010. Rates of emergency room visits involving opioids more than tripled from 1999 through 2013. 

In 2017, opioid overdose has been declared a national emergency in the United States.

Pathophysiology

Opioid medications bind to opioid receptors in the central and peripheral nervous systems (primarily delta, kappa, mu). These effects allow for effective treatment of pain, cough, and diarrhea. Action on these same receptors leads to intense euphoria which leads individuals to attempt to recreate that first high. Most people who misuse opioids do so chiefly for pain relief. However increasing evidence is dispelling the myth that opioids are effective long-term analgesic medications.

Below are receptors matched to physiologic effects (nociceptin and zeta receptors increasingly being researched):

  • Delta: analgesia, antidepressant, convulsant, physical dependence, modulate mu-related respiratory depression
  • Kappa: analgesia, anticonvulsant, depression, hallucination, diuresis, dysphoria, miosis, neuroprotection, sedation
  • Mu: analgesia, physical dependence, respiratory depression, miosis, euphoria, reduced GI motility, vasodilation

Withdrawal symptoms manifest when opioids are discontinued abruptly, though these can occur with tapered cessation of medications. Withdrawal symptoms can be divided into acute, subacute, and chronic phases. Most healthcare providers are aware of the acute withdrawal symptoms: hot/cold flashes, vomiting, sweating, lacrimation, insomnia, anxiety, dehydration.

Histopathology

Chronic opioid use does cause alterations in receptor sensitivity, leading to medication tolerance. Additionally, changes in pain perception occur in those on chronic opioids. Opioid induced hyperalgesia causes out of proportion pain perception in patients who use or misuse opioids on a long-term basis.

Toxicokinetics

The toxicokinetics of opioid drugs varies within the class. Half lives range from minutes in heroin injections to hours in methadone ingestion. Potencies of opioids also vary drastically, with more potent synthetic drugs such as fentanyl, carfentanil and newer compounds causing overdose deaths and necessitating large doses of naloxone for reversal.

Opioids tend to be lipophilic and metabolized in the liver by both phase 1 (modification) and phase 2 (conjugation) reactions.

History and Physical

History and physical examination in patients with opioid use disorder vary depending on duration and intensity of use. Patients who sporadically misuse small doses of opioids may have a completely normal physical exam and no clear historical findings. Patients with chronic oral opioid use may have sedation if actively using the drug, along with miosis on presentation, and hyperactive response to pain. 

Patients who are dependent on intravenous heroin may have the many effects of intravenous (IV) drug abuse:

  • Bacteremia
  • Endocarditis
  • Track marks and scarring in common sites of injection
  • Skin-popping scars
  • Poor dentition
  • Lack of IV access sites
  • Abscess or cellulitis
  • Stigmata of hepatitis
  • Cirrhosis, and many other findings.

History may be limited as patients are often not forthcoming when discussing substance abuse patterns. However, it is crucial to obtain detailed history in patients in whom opioid use disorder or its sequelae are suspected.

Evaluation

When opioid use disorder is suspected in a patient, the first step is a detailed history and physical exam. Patients often initially withhold information or may be outright dishonest or manipulative, depending on reasons for seeking medical attention.

As mentioned above, these patients are at risk for many secondary effects of drug abuse. Patients dependent on heroin are especially at risk for infectious complications. Therefore, many patients will need laboratory work and selected imaging depending on presenting symptoms.

Treatment / Management

Practitioners should offer patients who have an opioid use disorder inpatient or outpatient substance abuse treatment. The short-term treatment of new opioid prescriptions does not provide long-term benefit. Regulations limiting prescription of opioids are becoming more pervasive especially in the United States.

Patients presenting with opioid withdrawal often require antiemetic/antidiarrheal therapy and IV hydration. Opioid overdose should be promptly treated with naloxone to reverse the effects of the drug, particularly respiratory depression.

Medication assisted treatment (MAT) has shown promising results in the treatment of opioid use disorder. Nalbumetone, methadone, and naltrexone are used in various combinations and strategies to decrease abuse of both oral opioids and heroin. All patients at risk for overdose should have or receive naloxone kits for home use.

Pearls and Other Issues

Opioid use disorder has reached epidemic proportions both nationally and worldwide. Forty-nine US states have enacted prescription drug monitoring programs.

Other preventive treatments include good samaritan laws and naloxone distribution for overdose death prevention, harsher penalties for drug dealers, disincentives to the prescription of opioids, needle-exchanges to curtail infectious complications, and many emerging efforts.


References

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