Review of Deaths Related to Analgesic- and Cough Suppressant-opioids; England and Wales 1996-2002

Highlighting the hidden dangers of a 'weak' opioid: Deaths following use of dihydrocodeine in England (2001-2020)

BACKGROUND

Dihydrocodeine (DHC) is considered a 'weak' opioid, but there is evidence of its increasing misuse in overdose deaths. This research aims to analyse trends in DHC-related deaths in England relevant to source and dose of DHC, and decedent demographics.

METHODS

Cases from England reported to the National Programme on Substance Abuse Deaths (NPSAD) where DHC was identified at post-mortem and/or implicated in death between 2001 and 2020 were extracted for analysis.

RESULTS

2071 DHC-related deaths were identified. The greatest number of deaths involved illicitly obtained DHC and a significant increase in these deaths was recorded over time (r = 0.5, p = 0.03). However, there was a concurrent decline in the implication rate of DHC in causing death (r = -0.6, p < 0.01). Fatalities were primarily due to accidental overdose (64.8%) and misuse was highly prevalent in combination with additional central nervous system depressants (95.3%), namely illicit heroin/morphine and diazepam. In contrast, when DHC was obtained over-the-counter (OTC) suicide mortality accounted for almost half of the deaths (42.5%). Differences in polysubstance use were also identified, with less heroin/morphine and benzodiazepine co-detection, but increased OTC codeine co-detection.

CONCLUSIONS

DHC misuse in England is increasing. The pharmacological consideration of DHC as a 'weak' opioid may be misinterpreted by users, leading to accidental overdosing. There is an urgent need to understand increasing polypharmacy in overdose deaths. Additionally, suicides involving DHC is a potential cause for concern and a review of OTC opioid-paracetamol preparations is necessary to determine whether the benefits of these medications continue to outweigh the risks of intentional overdose.

Always Consider the Possibility of Opioid Induced Respiratory Depression in Patients Presenting with Hypercapnic Respiratory Failure Who Fail to Improve as Expected with Appropriate Therapy

Hypercapnic respiratory failure is a frequently encountered medical emergency. Two common causes are acute exacerbations of chronic obstructive pulmonary disease (COPD) and as a side effect of opioids. The two causes may coexist leading to diagnostic confusion and consequent delay in optimal management. We report a case of what was initially thought to be an exacerbation of COPD. The patient failed to improve with treatment as expected which led to the empirical administration of naloxone resulting in a dramatic reversal of her respiratory failure. The patient was subsequently discovered to be taking regular dihydrocodeine for chronic back pain.

Classical and novel psychoactive substances: rethinking drug misuse from an evolutionary psychiatric perspective

In this article, ontogenetic and phylogenetic causes of drug abuse and links to human emotional development are considered. Some evolutionary perspectives (e.g. that under certain conditions, consumption of otherwise toxic alkaloids may confer both physical and cultural advantages) are reviewed. As described in the 'mismatch theory', the capacity of the human genome to evolve defences against toxins has been outstripped by the pace of cultural change and technological development, such as purposeful fermentation of alcohol and more recently distillation of alcohol; purification and chemical manipulation of plant alkaloids; and the engineering of entirely novel psychoactive substances (NPS). The functions of the neurobiological substrates that mediate substance misuse and dependence are reviewed. Reasons are given why NPSs present greater cause for concern than plant-derived substances of abuse. We argue that evolutionary biology provides an important orientation for the research agenda in substance misuse.

A procedure that differentiates unintentional from intentional overdose in opioid abusers

OBJECTIVE

The purpose of this study is to develop a procedure for assessing unintentional overdose (OD) in opiate abusers that differentiates it from intentional OD, and provides reliable information about the incident.

METHODS

A sample of 121 patients in a methadone maintenance program at an urban university hospital completed a baseline assessment. A total of 70 participants completed an identical assessment at least 14 days later. The ability of an OD item to differentiate unintentional OD from intentional OD was tested, as was the test-retest reliability of questions assessing symptoms and treatment of OD.

RESULTS

The procedure is reliable and differentiated unintentional OD from intentional OD. Questions assessing symptoms of OD were endorsed in almost every unintentional OD incident, although reliability was affected by loss of consciousness. The reliability of questions assessing emergency treatment and Narcan administration was outstanding.

CONCLUSIONS

Our procedure for assessing OD differentiates unintentional OD from intentional OD. The use of follow-up questions assessing acute treatment for OD is recommended. Items concerning symptoms of OD are not needed to confirm the presence of an OD, but may be used to clarify whether an event was an OD.

Deaths of opiate/opioid misusers involving dihydrocodeine, UK, 1997-2007

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Dihydrocodeine (DHC) is an opioid analgesic sometimes prescribed as an alternative to other medications (e.g. methadone and buprenorphine) for opioid misuse. Its effectiveness is, however, still controversial. DHC prescription rates seem to be related to levels of DHC fatalities, possibly in relation to levels of disregard of the availability of supervised or interval dispensing of opioids, but no large-scale analysis of DHC fatalities has been carried out. We analysed here involvement of DHC in fatalities that occurred between 1997 and 2007 among individuals with a history of opiate/opioid misuse reported to the National Programme on Substance Abuse Deaths (np-SAD).

WHAT THIS STUDY ADDS

DHC, either alone or in combination, was identified in 584 fatalities. Typical cases identified were males in their early thirties. In accidental overdoses, DHC, which had been prescribed to 45% of the victims, was typically identified in combination with other drugs, such as heroin/morphine, methadone and hypnotics/sedatives. Both paracetamol and antidepressants were more typically identified in combination with DHC in suicides. Opiate/opioid misusers should be educated about risks associated with polydrug intake and prescribers should carefully consider a pharmacological intervention alternative to DHC (e.g. methadone, buprenorphine) when managing and treating opiate addiction.

AIMS

Although its effectiveness is somewhat controversial, it appears that dihydrocodeine (DHC) is still prescribed in the UK as an alternative to both methadone and buprenorphine for the treatment of opiate addiction.

METHODS

Data covering the period 1997-2007 voluntarily supplied by coroners were analysed. All cases pertaining to victims with a clear history of opiate/opioid misuse and in which DHC, either on its own or in combination, was identified at post-mortem toxicology and/or implicated in death, were extracted from the database.

RESULTS

Dihydrocodeine, either alone or in combination, was identified in 584 fatalities meeting the selection criteria. In 44% of cases it was directly implicated in the cause of death. These cases represented about 6.8% of all opiate/opioid-related deaths during this period. Typical DHC cases identified were White males in their early thirties. Accidental deaths (96%) were likely to involve DHC in combination with other psychoactives, mainly heroin/morphine, hypnotics/sedatives and methadone. Both paracetamol and antidepressants were found in proportionately more suicide cases than in accidental overdoses. DHC had been prescribed to the decedent in at least 45% of cases.

CONCLUSIONS

Opiate/opioid misusers should be educated about risks associated with polydrug intake. More in particular, co-administration of DHC with heroin, methadone and benzodiazepines may increase the risk of accidental fatal overdose. Prescribers should carefully consider pharmacological intervention alternative to DHC (e.g. methadone, buprenorphine) when managing and treating opiate addiction. More resources are required to do prospective research in this area.

Suicide verdicts as opposed to accidental deaths in substance-related fatalities (UK, 2001-2007)

BACKGROUND

Substance-related deaths account for a great number of suicides.

AIM

To investigate levels and characteristics of suicide verdicts, as opposed to accidental deaths, in substance misusers.

METHODS

Psychological autopsy study of cases from the UK National Programme on Substance Abuse Deaths (np-SAD) during the period 2001-2007.

RESULTS

Between January 2001 and December 2007, 2108 suicides were reported to the np-SAD. Typical suicide victims were White and older than 50 (respectively 95% and 41% of cases). Medications, especially antidepressants (44%), were prescribed to 87% of victims. Significantly fewer suicide victims than controls presented positive blood toxicological results for illicit drugs (namely: cocaine, heroin, amphetamines, ecstasy-type drugs, cannabis, and GHB/GBL) and alcohol.

CONCLUSIONS

Suicide prevention programmes should devote specific attention to deaths among substance misusers who are at high risk of fatal intentional self-harm. Specific characteristics distinguish those at risk; caregivers should be better educated as to what these factors are. Limitations of the current study included lack of provision of comprehensive information relating to the victims' psychosocial variables. Furthermore, no differentiation between different classes of antidepressants in terms of involvement in suicide was here provided.

Unintentional overdose and suicide among substance users: a review of overlap and risk factors

Substance use is a risk factor for suicide, suicide attempts, and fatal and non-fatal overdose, but to date, little has been done to integrate the research on suicidal behavior and overdose among substance users. This study reviews the literature on suicide and overdose among substance users with the goal of illuminating the similarities and differences between these two events. A structured review resulted in 15 articles (describing 14 unique studies) published between 1990 and 2010 that examined both overdose and suicide in samples of substance users. There is some evidence that substance users who attempt suicide are more likely to report an overdose and vice versa. This relationship may be partially explained by the fact that overdose is a common method of suicide. The results of the literature review also indicate that substance users with a history of both events may represent a group with particularly poor psychological and social functioning and severe drug-related problems. Further research is needed to understand the overlap of, and differences between, suicide and accidental overdose among individuals who misuse substances, particularly individuals who primarily use substances other than heroin. An improved understanding of the interrelationships between suicide and unintentional overdose among individuals who use alcohol or drugs is necessary to guide the development of effective prevention and intervention approaches.

Opioid microinjection into raphe magnus modulates cardiorespiratory function in mice and rats

The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with respiration-related discharge. Here, we asked whether RM contributes to respiratory depression, the most prevalent lethal effect of opioids. To investigate whether opioidergic transmission in RM produces respiratory depression, we microinjected a mu-opioid receptor agonist, DAMGO, or morphine into the RM of awake rodents. In mice, opioid microinjection produced sustained decreases in respiratory rate (170 to 120 breaths/min), as well as heart rate (520 to 400 beats/min). Respiratory sinus arrhythmia, indicative of enhanced parasympathetic activity, was prevalent in mice receiving DAMGO microinjection. We performed similar experiments in rats but observed no changes in breathing rate or heart rate. Both rats and mice experienced significantly more episodes of bradypnea, indicative of impaired respiratory drive, after opioid microinjection. During spontaneous arousals, rats showed less tachycardia after opioid microinjection than before microinjection, suggestive of an attenuated sympathetic tone. Thus, activation of opioidergic signaling within RM produces effects beyond analgesia, including the unwanted destabilization of cardiorespiratory function. These adverse effects on homeostasis consequent to opioid microinjection imply a role for RM in regulating the balance of sympathetic and parasympathetic tone.

Adverse drug interactions involving common prescription and over-the-counter analgesic agents

BACKGROUND

Eight analgesic preparations with approved indications for acute pain were among the top 200 drugs prescribed in the United States in 2006. In addition, an estimated 36 million Americans use over-the-counter (OTC) analgesics daily. Given this volume of use, it is not surprising that a number of drug interactions involving analgesic drugs have been reported.

OBJECTIVES

This article examines the pharmacologic factors that enhance the clinical relevance of potential drug interactions and reviews the literature on drug interactions involving the most commonly used analgesic preparations in the United States.

METHODS

A PubMed search was conducted for English-language articles published between January 1967 and July 2007. Among the search terms were drug interactions, acetaminophen, aspirin, ibuprofen, naproxen, celecoxib, NSAIDs, hydrocodone, oxycodone, codeine, tramadol, OTC analgesics, alcohol, ethanol, antihypertensive drugs, methotrexate, warfarin, SSRIs, paroxetine, fluoxetine, sertraline, citalopram, serotonin syndrome, MAOIs, and overdose. Controlled clinical trials, case-control studies, and case reports were included in the review.

RESULTS

A number of case reports and well-controlled clinical trials were identified that provided evidence of the relatively well known drug-drug interactions between prescription/OTC NSAIDs and alcohol, antihypertensive drugs, high-dose methotrexate, and lithium, as well as between frequently prescribed narcotics and other central nervous system depressants. In contrast, the ability of recent alcohol ingestion to exacerbate the hepatotoxic potential of therapeutic doses of acetaminophen is not supported by either case reports or clinical research. Use of ibuprofen according to OTC guidelines in patients taking cardioprotective doses of aspirin does not appear to interfere with aspirin's antiplatelet activity, whereas chronic prescription use of ibuprofen and other NSAIDs may interfere. Low-dose aspirin intake appears to abolish the gastroprotective effects of cyclooxygenase-2-selective inhibitors, including celecoxib. There is evidence of other less well known and potentially clinically significant drug-drug interactions, including the ability of selective serotonin reuptake inhibitors to inhibit the analgesic activity of tramadol and codeine through inhibition of their metabolic activation, to induce serotonin syndrome when used chronically in the presence of high doses of tramadol through synergistic serotonergic action, and to increase the potential for gastrointestinal bleeding associated with NSAID therapy through additive or supra-additive antiplatelet activity.

CONCLUSIONS

Considering the widespread use of analgesic agents, the overall incidence of serious drug-drug interactions involving these agents has been relatively low. The most serious interactions usually involved other interacting drugs with low therapeutic indices or chronic and/or high-dose use of an analgesic and the interacting drug.