Opioid analgesics, also called narcotics, are drugs usually used for treating pain. Opioid analgesics are defined as "all of the natural and semisynthetic alkaloid derivatives from opium, their pharmacologically similar synthetic surrogates, as well as all other compounds whose opioid-like actions are blocked by the nonselective opioid receptor antagonist naloxone.[1]
There a several opioid receptors. All are G-protein-coupled cell surface receptors. Clinically useful analgesic families vary in their receptor effects; they range from pure agonists of all receptor types, to selective agonists, to agonist-antagonists.
Tables of morphine equivalent daily dose and IV to PO conversion are available to help dosing, although direct conversion is unwise with opioids with complex pharmacodynamics, such as methadone.
A number of oral forms are combined with acetaminophen to reduce the possibility of diversion to injected abuse, although acetaminophen also has a distinct and potentially synergistic analgesic effect. Acetaminophen has been found to be more toxic, with or without opioids, than had been generally believed, and the FDA has recommended restrictions on its uses.[7][6]
The American Pain Foundation is concerned that these recommendations consider the matter carefully, lest there be undertreatment with appropriate opioids. [8] Combination with aspirin and other non-narcotic agents was common before the widespread use of acetaminophen
Oxycodone may increase mortality relative to codeine and hydrocodone[13] and may cause more drug toxicity in geriatrics than codeine or hydrocodone.[13]
Opioids are commonly prescribed for pain, and their usage may be increasing.[17] In emergency rooms, non-Hispanic white patients are more likely to receive narcotics than patients of other ethnicities.[17]
Opioids are effective for short term use (1-16 weeks)[18].
For chronic, non-cancer pain, opioids may give short term reduction in pain compared to placebo.[19][20][21]
The role of long term treatment of chronic non-cancer pain is not clear.
A systematic review by the Cochrane Collaboration found "weak evidence suggests that patients who are able to continue opioids long-term experience clinically significant pain relief. Whether quality of life or functioning improves is inconclusive."[22]
One systematic review found that trials of short term opioids did not improve functional status compared to placebo in chronic pain.[19] However, a second systematic review, found that opioids improved functional status compared to placebo, but not compared to other drugs.[21]
Tables of morphine equivalent daily dose and IV to PO conversion are available to help dosing, but must be used with caution. Some opioids, such as methadone, do not lend themselves to simple conversion due to greatly differing half-lives. While an antagonist or partial antagonist may have equianalgesic dosing in an opioid-naive patient, switching from, for example, long-term morphine to buprenorphine can cause withdrawal.
Most opioids can be administered parenterally. Recent developments have provided alternate formulation that improve oral effectiveness of drugs historically injected, such as morphine.
Novel routes are being found effective, such as transdermal skin patches that provide a constant low-rate dose, and transmucosal and intranasal routes for quick action.
Fear of addiction had long interfered with the extended use of opioids even in terminal patients. Current practice, however, includes the indefinite use of opioids in nonterminal patients with pain that can only be controlled by opioids. The World Health Organization, for example, has a "pain pyramid" for rheumatic disease, which begins with acetaminophen or equivalents, and moves to increasingly powerful opioids. Long-term opioid therapy is prescribed both for analgesia, and also the treatment of opioid dependence.
Mortality may be increased upon both starting and topic opioid maintenance.[27]
Advice for using administering chronic narcotics[26] and for treating acute pain among patients on chronic methadone is available[28]. Special technique may also be needed for patients receiving buprenorphine for chronic pain.
There are challenges in prescribing opioids with specialized actions, such as partial agonists and mixed agonist/antagonists. These may interfere with the effectiveness of breakthrough medications for additional acute pain. Such drugs also may be ineffective or produce withdrawal in patients receiving other long-term opioids.
Opioid treatment agreements and urine drug testing may reduce opioid misuse by patients with chronic pain. [31] Urine drug testing is of two types:[32]
Immunoassay. Immunoassay is available rapidly and at the point of care, but does not reliably detect semisynthetic and synthetic opioids.
Opioid analgesics, with long-term use, 80% of patients may have drug toxicity, most commonly gastrointestinal. In addition, substance abuse and "aberrant medication-taking behaviors" may occur.[20]
Serious drug toxicity from long-term use may be low according to one systematic review.[22]
Dietary agents and inert physical agents may help. A high-fiber diet is desirable, possibly with fiber supplements such as psyllium and metacellulose. The stool softener docusate is often prescribed. Stronger laxatives are not desirable.
Number of Poisoning Deaths Involving Opioid Analgesics and Other Drugs or Substances --- United States, 1999--2007.
Death from overdose on opioids may be more common than traffic accidents in the United States.[47] The rate of overdose is increasing faster among women and men according to the Centers for Disease Controll.[48]
Chronic use of the equivalent of more than 20 mg/day of morphine may lead to unintentional or intentional overdose.[49]
Overdose may be more common with with doses equivalent to more than 100 mg/day of morphine.[50] Overdose may[51] or may not[50] be increased with long acting opioids.
In veterinary medicine, there is a maximum effective analgesic dose of buprenorphine, although the frequency of administration may usefully be increased.[52]
With chronic use for treatment of pain, dependency may lead to substance abuse and "aberrant medication-taking behaviors" may occur.[20] From 2000-2005, the abuse of prescribed opiods, especially oxycodone extended release (OxyContin) and hydrocodone, has increased.[53] From Contracts may reduce abuse, but comparative studies provide conflicting results.[54] Most agreements stated, "patients agreed not to abuse illicit drugs or alcohol, obtain opioids from more than 1 provider or pharmacy, or request a refill before the previous prescription should have been completed."
Pruritis from histamine release may occur.[58] Anecdotally, one of the reason for using antihistamines as adjuvants, such as hydroxyzine and promethazine, are to alleviate some of these side effects, as well as nausea. The less sedating hydroxyzine also may potentiate analgesia and have a better antipruritic effect although promethazine may be stronger against nausea.
↑ 17.017.1Pletcher MJ, Kertesz SG, Kohn MA, Gonzales R (2008). "Trends in opioid prescribing by race/ethnicity for patients seeking care in US emergency departments". JAMA299 (1): 70–8. DOI:10.1001/jama.2007.64. PMID 18167408. Research Blogging.
↑Chou R, Deyo R, Devine B, Hansen R, Sullivan S, Jarvik JG, Blazina I, Dana T, Bougatsos C, Turner J. The Effectiveness and Risks of Long-Term Opioid Treatment of Chronic Pain. Evidence Report/Technology Assessment No. 218. (Prepared by the Pacific Northwest Evidence-based Practice Center under Contract No. 290-2012-00014-I.) AHRQ Publication No. 14-E005-EF. Rockville, MD: Agency for Healthcare Research and Quality; September 2014. The Effectiveness and Risks of Long-Term Opioid Treatment of Chronic Pain. Evidence Report/Technology Assessment No. 218. (Prepared by the Pacific Northwest Evidence-based Practice Center under Contract No. 290-2012-00014-I.) AHRQ Publication No. 14-E005-EF. Rockville, MD: Agency for Healthcare Research and Quality; September 2014.
↑Moulin DE, Iezzi A, Amireh R, Sharpe WK, Boyd D, Merskey H (1996). "Randomised trial of oral morphine for chronic non-cancer pain.". Lancet347 (8995): 143-7. PMID 8544547.
↑Raja SN, Haythornthwaite JA, Pappagallo M, Clark MR, Travison TG, Sabeen S et al. (2002). "Opioids versus antidepressants in postherpetic neuralgia: a randomized, placebo-controlled trial.". Neurology59 (7): 1015-21. PMID 12370455. [e]Review in: J Fam Pract. 2003 Jul;52(7):517-8
↑Cornish R et al. (2010) Risk of death during and after opiate substitution treatment in primary care: prospective observational study in UK General Practice Research Database. BMJ 2010; 341:c5475 DOI:10.1136/bmj.c5475
↑Orriols L, Delorme B, Gadegbeku B, Tricotel A, Contrand B, et al. 2010 Prescription Medicines and the Risk of Road Traffic Crashes: A French Registry-Based Study. PLoS Med 7(11): e1000366. DOI:10.1371/journal.pmed.1000366