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Drug interactions of clinical significance with opioid analgesics.

Opioid analgesics and other drugs interact through multiple mechanisms, resulting in pharmacological effects that depend upon the pharmacodynamic action studied, the interacting agents and the route of administration. Many interactions result from induction or inhibition of the hepatic cytochrome P450 mono-oxygenase system. The elimination of opioids is largely dependent on hepatic metabolism, and drug interactions involving this mechanism can therefore be clinically significant. Antibiotics are often used concomitantly with opioids in patients undergoing medical or surgical procedures; the best documented metabolic interactions are with erythromycin and rifampicin (rifampin). Erythromycin increases and rifampicin decreases the effects of opioids. Cimetidine may increase the effects of opioids by increasing their duration of action; there have been no documented cases of interactions with ranitidine. Carbamazepine, phenytoin and the barbiturates can enhance the metabolism of opioids that rely on hepatic metabolism. Other pharmacokinetic interactions include those with benzodiazepines, tricyclic antidepressants, phenothiazines and metoclopramide. Interactions involving pharmacodynamic mechanisms are more common than pharmacokinetic ones. Such interactions are manifested clinically as as a summation (additive or synergistic) of similar or opposing pharmacological effects on the same body system. Idiosyncratic interactions also occur, the mechanisms of which have not been proven to be solely modulated by either pharmacokinetic or pharmacodynamic means. The knowledge of particular opioid-drug interactions, and the causative pharmacokinetic, pharmacodynamic, and idiosyncratic mechanisms, allows for the safer administration of opioid analgesics.

Analgesics↗

Clinical pharmacology of opioid analgesics.

Opioid analgesics continue to be the most important drugs in modifying the response to pain. Their versatility is attested by their frequent use in both postoperative and intraoperative management of pain. Recent findings regarding the mechanism of action of opioids may signal the introduction of newer, more effective, and less addictive agents. So far, this has not occurred. However, opioids with mixed agonist-antagonist properties have offered some utility. The adverse effects of nausea and dysphoria and the more serious effects of respiratory depression continue to be a problem, as does the possibility of abuse. Nonetheless, the clinical experience with opioids in control of pain is uncontested. Until better drugs are developed, opioids will form the basis for the control of acute pain by the dental practitioner.

Adult↗

Opioid analgesics.

Opioids are useful and potent drugs for the management of pain in small animal patients. They have a wide therapeutic index and can be given by a number of different routes. Some of these techniques (e.g., epidural and intraarticular) allow for the production of profound analgesia in a localized area of the body while limiting the dose and the side effects, and others provide a noninvasive method for the delivery of continuous analgesia (e.g., transdermal administration).

Analgesics, Opioid↗

Opioid and non-opioid analgesics.

Opioids are the most potent analgesics. Toxicity results either from effects mediated by variation in affinity and intrinsic efficacy at specific opioid receptors or, rarely, from a direct toxic effect of the drugs. For some adverse effects, opioids exhibit a 'dual pharmacology' whereby these effects are usually observed only in pain-free individuals, and are not seen in patients in pain. Paracetamol, although generally very safe in therapeutic doses, displays potentially fatal toxicity in overdose requiring specific treatment. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to act by inhibiting COX-1 and COX-2 isoenzymes to various degrees. Toxicity arises primarily from undesired inhibition at these enzyme sites. Knowledge of the mechanism of action of these drugs is fundamental to the understanding of their potential for toxicity, the details of which are still emerging.

Acetaminophen↗

Prevalence of opioid analgesic injection among rural nonmedical opioid analgesic users.

OBJECTIVE: The purpose of this study was to examine the prevalence and correlates of opioid analgesic injection (OAI) in a cohort of rural opioid analgesic users. METHODS: Cross-sectional study of 184 participants from rural Appalachian Kentucky. RESULTS: The majority of participants were male (54.9%), white (98.4%) and the median age was 30 years (interquartile range: 24-37). The self-reported lifetime prevalence of injection drug use (IDU) was 44.3%, with 35.3% of respondents reporting injection of oral opioid analgesic formulations. The prevalence of self-reported hepatitis C (HCV) was 14.8%, significantly greater than those not injecting opioid analgesics (1.7%) (p<0.001). Receptive needle sharing, distributive needle sharing and sharing of other injection paraphernalia was reported by 10.5%, 26.3%, and 42.1% of those currently injecting, respectively. CONCLUSIONS: Opioid analgesic injection was more prevalent in this rural population than has been found in previous reports. This study suggests a rising problem with injecting among rural opioid users, a problem more typically associated with urban drug users. Educating injectors of opioid analgesics on safe needle practices is necessary in order to curb the transmission of HIV, HCV, and other infectious diseases. Further study on the longitudinal course of opioid analgesic injection in this population appears warranted.

Adult↗

Supersensitivity to opioid analgesics following chronic opioid antagonist treatment: relationship to receptor selectivity.

The effect of chronic opioid antagonist treatment on the analgesic potency of six opioid agonists was compared to changes in opioid receptor density and the selectivity of each agonist for mu (DAMGO), delta (DPDPE) and kappa (U69,593) opioid receptors. Mice were implanted SC with a 15-mg naltrexone or placebo pellet for 8 days. The pellets were removed and 24 h later, mice were sacrificed and binding studies were conducted, or mice were tested in analgesia (tail-flick) dose-response studies. All six analgesics acted as full agonists for both placebo and naltrexone-treated mice. Naltrexone increased the analgesic potency of methadone, etorphine, fentanyl, meperidine, and oxycodone by 1.9-3.2-fold. The analgesic potency of propoxyphene was not increased significantly (1.3-fold). In saturation binding studies in brain homogenate, naltrexone increased the Bmax of mu, delta, and kappa opioid receptors by 86, 43, and 33%, respectively, without altering Kd. Competition binding studies for each receptor type were conducted in brains from untreated mice, and KIs were determined for each agonist. All agonists had greatest selectivity toward mu compared with delta and kappa receptors. There did not appear to be an obvious relationship between receptor selectivity and the magnitude of supersensitivity. These studies indicate that supersensitivity occurs for a broad range of opioid analgesics following chronic opioid antagonist treatment in the mouse. However, the selectivity of these agonists for mu, delta, and kappa receptors does not appear to correlate with differences in supersensitivity.

Analgesics↗

A survey of chronic noncancer pain patients prescribed opioid analgesics.

OBJECTIVES: Opioid analgesic drugs are sometimes advocated for chronic noncancer pain (CNCP). However, due to the paucity of studies assessing problematic opioid drug use in this population, evidence for such is inconclusive, and this issue remains controversial. This survey assessed problematic drug use among CNCP patients. PATIENTS/SETTING: Patients (N=104) prescribed opioids (mean duration of treatment 14.1 months) for severe CNCP at a pain clinic within a National Health Service hospital in London, United Kingdom. DESIGN: A review of pain clinic records to identify CNCP patients who had been prescribed opioids and subsequent assessment of those patients for problematic drug use using a substance use questionnaire. RESULTS: A total of 90 (86.5%) patients reported stopping opioid therapy at some point and, of these, 59 (65%) had ceased opioid therapy permanently. Of those patients who stopped opioids, 13 reported opioid withdrawal symptoms, two with severe and two with very severe symptoms. However, 72.5% of all patients derived benefit from opioids, although 77% of all patients reported opioid side effects. The addiction rate was 2.8%. CONCLUSION: These findings indicate that opioid therapy for CNCP does not necessarily lead to problematic drug use. Some problematic side effects are likely to be surmountable through appropriate prescribing. Further research is required into the long-term use of opioids in CNCP.

Adult↗

Comparison of the ability of opioid analgesics to increase endogenous opioid-like activity in the cerebrospinal fluid of rabbits.

We have previously demonstrated that the acute administration of morphine increases the level of endogenous substances, which have antinociceptive activity, in cerebrospinal fluid (CSF). The present study was conducted to determine whether other opioid analgesics exert a similar effect. CSF was withdrawn from the cisterna magna of anesthetized rabbits before and after s.c. injections of meperidine, pentazocine, levorphanol and methadone, and was bioassayed for opioid-like activity in the mouse tail-flick and phenylquinone writhing tests. The opioid-like activity of CSF taken 60 min after meperidine (50 mg/kg) was significantly increased in both bioassays, and the CSF level of meperidine was insufficient to account for this effect. Pentazocine (25-75 mg/kg) also significantly increased opioid-like activity in rabbit CSF, but the effects of methadone (5-10 mg/kg) and levorphanol (20 mg/kg) were less marked. Dextrorphan (20 mg/kg), diazepam (10 mg/kg) and pentobarbital (20 mg/kg) administration did not significantly increase opioid-like activity in CSF. It is concluded that the antinociceptive action of some opioid analgesics in rabbits may be mediated in part by the release of endogenous antinociceptive substances.

Animals↗

Adverse effects of opioid analgesic drugs.

Opioids were available in clinical practice since before the birth of modern anaesthesia--Setürner isolated morphine in 1806. They have a record of safety which is reflected in their high therapeutic ratios, especially the synthetic opioids introduced recently (table III). The most serious immediate adverse effect, respiratory depression, is a predictable effect related closely to analgesia. It is fortunate for anaesthetists who use opioids regularly, that recognition and treatment of respiratory problems are an integral part of their craft and that opioid antagonists are effective in reversing respiratory depression.

Analgesics, Opioid↗

Using opioid analgesics to manage chronic noncancer pain in primary care.

BACKGROUND: Opioid analgesics have been considered the drugs of choice for the treatment of moderate to severe cancer and postoperative pain. Cultural attitudes and concerns about abuse have inhibited their use for a larger population of patients who have chronic noncancer pain. METHODS: Medical literature was searched from 1990 to 1998 using the key words "opioid analgesics," "opioid abuse," and "chronic pain." I have also drawn from more than 20 years of experience prescribing opioid analgesics for chronic pain. A case series analysis of 30 patients using opioid analgesics for periods ranging from 6 months to 17 years was performed. RESULTS AND CONCLUSIONS: The World Health Organization has published a "three-step ladder" guide to treatment of cancer pain graded from mild to severe; this guide can be readily applied to the treatment of pain from all sources. Opioid analgesics are the mainstay of treatment for moderate to severe pain. Chronic pain patients offer some difficult challenges for busy primary care physicians. The unique pharmacologic characteristics of opioid medications are important in outpatient management. A four-sheet office management protocol helps to focus efficiently on important clinical issues related to pain control, to monitor for opiate abuse, and to incorporate pain management more effectively in the overall primary care plan of the patient.

Adult↗

[Non-opioid analgesics in cancer pain].

Non-opioid analgesics such as NSAIDs play a central role for patients with cancer pain as well as for those with acute pain. Pain management using non-opioid analgesics need to avoid potential side effects, and the analgesic action of NSAIDs, cyclooxygenase inhibitors, would synergistically potentiate opioids' effects via the activation of the periaquaductal grey of the midbrain. The analgesic action of opioids would also be potentiated by the activation of alpha 2-adrenoceptors of the spinal cord. Thus the use of non-opioid analgesics for cancer patients taking opioid needs meticulous care. Undertreatment of pain is a persistent clinical problem for patients with cancer. Although changing medical practice is difficult and improving pain management with the rational use of combination of drugs may especially difficult, supplementation of non-opioid analgesics for opioid treatment would provide a better quality of life of cancer patients.

Adrenergic alpha-Agonists↗

G-protein receptor kinase 3 (GRK3) influences opioid analgesic tolerance but not opioid withdrawal.

1. Tolerance to opioids frequently follows repeated drug administration and affects the clinical utility of these analgesics. Studies in simple cellular systems have demonstrated that prolonged activation of opioid receptors produces homologous receptor desensitization by G-protein receptor kinase mediated receptor phosphorylation and subsequent beta-arrestin binding. To define the role of this regulatory mechanism in the control of the electrophysiological and behavioral responses to opioids, we used mice having a targeted disruption of the G-protein receptor kinase 3 (GRK3) gene. 2. Mice lacking GRK3 did not differ from wild-type littermates neither in their response latencies to noxious stimuli on the hot-plate test nor in their acute antinociceptive responses to fentanyl or morphine. 3. Tolerance to the electrophysiological response to the opioid fentanyl, measured in vitro in the hippocampus, was blocked by GRK3 deletion. In addition, tolerance to the antinociceptive effects of fentanyl was significantly reduced in GRK3 knockouts compared to wild-type littermate controls. 4. Tolerance to the antinociceptive effects of morphine was not affected by GRK3 deletion although morphine tolerance in hippocampal slices from GRK3 knockout mice was significantly inhibited. Tolerance developed more slowly in vitro to morphine than fentanyl supporting previous work in in vitro systems showing a correlation between agonist efficacy and GRK3-mediated desensitization. 5. The results of these studies suggest that GRK3-mediated mechanisms are important components of both electrophysiologic and behavioral opioid tolerance. Fentanyl, a high efficacy opioid, more effectively produced GRK3-dependent effects than morphine, a low efficacy agonist.

Analgesics, Opioid↗

Illicit use of opioid analgesics by high school seniors.

The illicit use of opioid analgesics represents a growing problem among American adolescents. In order to examine the correlates associated with the illicit use of opioid analgesics, a nationally representative sample of 4,522 high school seniors from the 2002 Monitoring the Future database was examined. Multivariate logistic regression indicated that illicit users of prescription opioid analgesics were significantly more likely to be male, White, and have lower grade point averages. Illicit users of opioid analgesics also reported higher rates of cigarette smoking, alcohol use, marijuana use, other illicit drug use, and problem behaviors. The present study provides evidence that the illicit use of opioid analgesics represents a problem among American high school seniors and effective prevention and intervention efforts are needed.

Adolescent↗

The changing role of non-opioid analgesic techniques in the management of postoperative pain.

Given the expanding role of ambulatory surgery and the need to facilitate an earlier hospital discharge, improving postoperative pain control has become an increasingly important issue for all anesthesiologists. As a result of the shift from inpatient to outpatient surgery, the use of IV patient-controlled analgesia and continuous epidural infusions has steadily declined. To manage the pain associated with increasingly complex surgical procedures on an ambulatory or short-stay basis, anesthesiologists and surgeons should prescribe multimodal analgesic regimens that use non-opioid analgesics (e.g., local anesthetics, nonsteroidal antiinflammatory drugs, cyclooxygenase inhibitors, acetaminophen, ketamine, alpha 2-agonists) to supplement opioid analgesics. The opioid-sparing effects of these compounds may lead to reduced nausea, vomiting, constipation, urinary retention, respiratory depression and sedation. Therefore, use of non-opioid analgesic techniques can lead to an improved quality of recovery for surgical patients.

Ambulatory Surgical Procedures↗

[Non-opioid analgesics for perioperative pain therapy. Risks and rational basis for use].

Non-opioid analgesics play a central role in the management of postoperative pain. In this review, the pharmacology, the analgesic efficacy and the side-effects of non-opioid analgesics are summarized. First, the pharmacology of diclofenac, acetyl salicylic acid, dipyrone, acetaminophen and the COX-2 inhibitors is described. Second, the analgesic efficacy of non-opioid analgesics is analyzed for moderate pain (e.g. ambulatory surgery) and for moderate to severe pain (e.g. abdominal surgery-in combination with opioids). There is limited evidence for an additive analgesic effect of two non-opioid analgesics. Third, the major side-effects of non-opioid analgesics are discussed in relation to the pathophysiology, the frequency and the clinical relevance of these effects. In particular, side-effects on the gastrointestinal tract (ulcus formation), on coagulation (bleeding and thrombosis), on the renal (renal insufficiency), the pulmonary (bronchospasm) and the hematopoetic systems (agranulocytosis) are described. Recommendations for the clinical use of non-opioid analgesics for perioperative pain therapy are given.

Acute Kidney Injury↗

Trends in medical use and abuse of opioid analgesics.

CONTEXT: Pain often is inadequately treated due in part to reluctance about using opioid analgesics and fear that they will be abused. Although international and national expert groups have determined that opioid analgesics are essential for the relief of pain, little information has been available about the health consequences of the abuse of these drugs. OBJECTIVE: To evaluate the proportion of drug abuse related to opioid analgesics and the trends in medical use and abuse of 5 opioid analgesics used to treat severe pain: fentanyl, hydromorphone, meperidine, morphine, and oxycodone. DESIGN AND SETTING: Retrospective survey of medical records from 1990 to 1996 stored in the databases of the Drug Abuse Warning Network (source of abuse data) and the Automation of Reports and Consolidated Orders System (source of medical use data). PATIENTS: Nationally representative sample of hospital emergency department admissions resulting from drug abuse. MAIN OUTCOME MEASURES: Medical use in grams and grams per 100,000 population and mentions of drug abuse by number and percentage of the population. RESULTS: From 1990 to 1996, there were increases in medical use of morphine (59%; 2.2 to 3.5 million g), fentanyl (1168%; 3263 to 41,371 g), oxycodone (23%; 1.6 to 2.0 million g), and hydromorphone (19%; 118,455 to 141,325 g), and a decrease in the medical use of meperidine (35%; 5.2 to 3.4 million g). During the same period, the total number of drug abuse mentions per year due to opioid analgesics increased from 32,430 to 34,563 (6.6%), although the proportion of mentions for opioid abuse relative to total drug abuse mentions decreased from 5.1% to 3.8%. Reports of abuse decreased for meperidine (39%; 1335 to 806), oxycodone (29%; 4526 to 3190), fentanyl (59%; 59 to 24), and hydromorphone (15%; 718 to 609), and increased for morphine (3%; 838 to 865). CONCLUSIONS: The trend of increasing medical use of opioid analgesics to treat pain does not appear to contribute to increases in the health consequences of opioid analgesic abuse.

Analgesics, Opioid↗

Geographic variation in the prescription of schedule II opioid analgesics among outpatients in the United States.

OBJECTIVE: To measure geographic variation in opioid use in a large, commercially insured, outpatient population in the United States. DATA SOURCES: Outpatient prescription drug claims database of a national pharmaceutical benefit manager for 7,873,337 subjects with at least one prescription drug claim in 2000. STUDY DESIGN: We measured the period prevalence of claims for opioid analgesics and controlled-release oxycodone at the state level. We measured geographic variation using the weighted coefficient of variation and systematic component of variation. In county-level multivariable regression, we explored associations between potential explanatory variables and claims for opioid analgesics and controlled-release oxycodone. PRINCIPAL FINDINGS: A total of 567,778 (64.2 per 1,000 total claims) were for oral opioid analgesics. Claim rates by state ranged from <20 to >100 claims per 1,000 total claims. States with long-standing prescription monitoring programs had among the lowest rates. In the county-level data, presence of a statewide prescription monitoring program and proportions of the population aged 15-24 and 65 years and older were independently and negatively associated with claim rates for all opioid analgesics. Surgeons per 1,000, proportion of the population reporting illicit drug use, and proportion who were female were independently and positively associated with claim rates for all opioid analgesics. Only the proportion of the population aged 25-34 and number of surgeons per 1,000 were independently and positively associated with claim rates for oxycodone. CONCLUSIONS: Claim rates for opioid analgesics vary significantly by state. Presence of a statewide prescription monitoring program is associated with lower claim rates at the county level. Future research should use individual-level data to assess whether these findings reflect a reduction in abuse and diversion or suboptimal treatment of pain.

Adolescent↗

Evidence for and against the use of opioid analgesics for chronic nonmalignant low back pain: a review.

INTRODUCTION: Opioid analgesics are very effective for treating pain, but their chronic use in nonmalignant conditions is controversial. Low back pain is a common condition, and chronic low back pain (CLBP) is the most frequent regional pain syndrome in the United States. This article reviews the evidence for and against the use of chronic opioid analgesic therapy (COAT) for patients with CLBP unrelated to cancer. METHODS: A literature review was conducted looking for reports of oral or transdermal opioid analgesic therapy for CLBP. RESULTS: There are very few randomized controlled trials of COAT for CLBP. The scant evidence that is available suggests that over the short-term, COAT is helpful with patients with CLBP. In the published reports, most of which are brief in duration, COAT is associated with moderate side effects but a low risk of abuse or drug addiction. COAT was not associated with adverse long-term sequelae. Longer-acting opioid analgesics may be preferable to shorter-acting agents. Patient selection and close follow-up are critical to good outcomes. CONCLUSIONS: There is a place for the use of chronic oral or transdermal opioid analgesics in the treatment of some patients with CLBP.

Journal Article↗