Dextropropoxyphene overdose. Epidemiology, clinical presentation and management

Neurotoxic emergencies

This article is intended for clinicians treating neurotoxic emergencies. Presented are causative agents of neurotoxic emergencies, many of which are easily mistaken for acute psychiatric disorders. Understanding the wide variety of agents responsible for neurotoxic emergencies and the neurotransmitter interactions involved will help the psychiatrist identify and treat this challenging population.

Prevalence and correlates of epileptic seizure in substance-abusing subjects

Life-time prevalence of epileptic seizures was assessed in 626 consecutive patients treated for substance abuse. Seizures were reported in 8.63% (9.2% in alcohol abusers, 12.5% in opioid abusers). A total of 64.8% of the seizures were associated with substance use. These occurred during withdrawal in the alcohol cohort and during intoxication with dextropropoxyphene and withdrawal from heroin or poppy husk in the opioid cohort. Results indicate that seizures may be more common in older patients with longer duration of dependence among those abusing alcohol.

Chemically Induced Seizures

Drug- and toxin-associated seizures (DTS) may result from exposure to a wide variety of agents. Most DTS can be managed with supportive care. First-line anticonvulsant therapy should include benzodiazepines, unless agents require a specific antidote. Phenytoin is generally not expected to be useful for DTS and in some instances may be harmful. In this article the authors discuss the pathophysiology of DTS, the potential differential diagnosis, and the clinical presentation. They also review selected agents that cause DTS and provide an overview of how the clinician should approach the management of patients who have DTS.

Drug- and toxin-associated seizures

Drug- and toxin-associated seizures may result from exposure to a wide variety of agents. Obtaining a comprehensive history behind the exposure is generally more helpful than diagnostic testing. Most DTS may be managed with supportive care, including benzodiazepines, except in the case of agents that require a specific intervention or antidote.

A multicentre study of coproxamol poisoning suicides based on coroners' records in England

AIMS

To examine in detail a series of coproxamol overdose deaths in order to provide information that will assist in the development of strategies to prevent such fatalities.

METHOD

Inquest records in 24 coroners' jurisdictions in England on deaths between January 2000 and December 2001 which received a verdict of either suicide or undetermined cause (with a high or moderate probability of suicide) were examined.

RESULTS

One hundred and twenty-three coproxamol poisoning suicides were identified. Alcohol was involved in 58.5% of the overdoses and these individuals generally had lower blood drug levels and consumed fewer tablets. Younger people were more likely to have consumed alcohol and to have lower levels of suicide intent. Nearly half the individuals had a history of self harm, and a third were under psychiatric care. The coproxamol had been prescribed for the individual in 81.5% of cases, although only in 55.0% of those aged 10-34 years. In other cases the source of the coproxamol was nearly always a family member or partner. Some deaths resulted from relatively small overdoses.

CONCLUSIONS

Strategies to reduce self poisoning deaths due to coproxamol should take account of the high toxicity of coproxamol in overdose, especially when combined with alcohol, and the fact that risk of death extends beyond the person for whom the drug is prescribed.

Co-proxamol and suicide: preventing the continuing toll of overdose deaths

Restricting means for suicide is a key element in suicide prevention strategies of all countries where these have been introduced. Preventing deaths from analgesic overdoses is highlighted in the National Suicide Prevention Strategy for England. The problem of self-poisoning with the prescription-only drug co-proxamol (dextropropoxyphene plus paracetamol) has received attention in several countries. We have conducted a review of the international literature related to possible strategies to tackle this problem. In England and Wales in 1997-1999, 18% of drug-related suicides involved co-proxamol; these constituted 5% of all suicides. Death usually results from the toxic effects of dextropropoxyphene on respiration or cardiac function. Death from co-proxamol overdose may occur rapidly, the lethal dose can be relatively low, and the effects are potentiated by alcohol and other CNS depressants. The majority of co-proxamol overdose deaths occur before hospital treatment can be received. The risk can extend to others in the household of the person for whom the drug is prescribed. While there is limited evidence that educational strategies have been effective in reducing deaths from co-proxamol poisoning, initiatives in Scandinavia, Australia and the UK to restrict availability of co-proxamol have produced promising results. Given the paucity of evidence for superior therapeutic efficacy of co-proxamol over other less toxic analgesics, there are good reasons to question whether it should continue to be prescribed.

Citalopram in fatal poisoning cases

Citalopram, a selective serotonin reuptake inhibitor, is the most frequently prescribed antidepressant in Sweden. To investigate the extent to which citalopram in overdose is found in fatal poisoning cases compared with other drugs, all fatal poisonings in one forensic medicine district in Sweden during the years 1994-1999 were examined. Drugs found in overdose in more than 10 cases were included. The ratio between number of cases with each included drug and prescription of defined daily dose/1,000 inhabitants/day (DDD) was determined. Citalopram was the fourth most frequently found drug in overdose, occurring in 22 (6%) of the 358 fatal poisoning cases, after dextropropoxyphene (DXP), flunitrazepam and nitrazepam, which were present in 111 (31%), 56 (16%) and 31 (9%) cases, respectively. When related to the prescription rate, citalopram was significantly less represented than five of the other seven included drugs, namely DXP, flunitrazepam, nitrazepam, amitriptyline and clomipramine. Propiomazine and zopiclone occurred to the same extent as citalopram. According to the assessments of the forensic physicians, citalopram was the cause of death in five cases (1.4%) and contributed to death in another nine cases (2.5%). It is concluded that citalopram, in spite of its high prescription rate, has not become a drug of importance in fatal poisoning cases. Since, this result may not be generalisable to non-fatal poisoning cases, it is recommended that the prevalence of citalopram in these cases be examined separately.

Characteristics of suicide among children and adolescents in Budapest

BACKGROUND

In Europe, the suicide rate among children and adolescents is the highest in Hungary. In the young age group (10-14 and 15-19 years), the suicide mortality rate had not showed a decrease.

METHODS

This study examined suicide cases committed by children and adolescents highlighted from the extraordinary death cases in Budapest between 1994 and 1998. The 72 suicide cases, which included 59 males and 13 females, were processed by sex, age, method and time of commitment, and distribution by districts.

RESULTS

Leaping off high places or hanging was the highest frequency among the methods of commitment. Accurate data about the frequency, type, time and location of death cases are indispensable to decrease the number of children's and adolescents' suicides.

CONCLUSIONS

Studies of epidemiology and risk factors may provide a basis of development of a specific suicide prevention programme including educational, health and welfare elements.

Correlation between prescription of various dextropropoxyphene preparations and their involvement in fatal poisonings

In Sweden, the frequency of fatal poisoning by dextropropoxyphene (DXP) ingestion is constantly high. There are seven preparations containing DXP on the Swedish market; in three of them DXP is the sole analgesic ingredient, while four of them are combinations of analgesics. In an attempt to assess the death rate attributable to each DXP preparation on the basis of toxicological analyses, altogether 834 cases of dextropropoxyphene-related death over a 5-year period (1992-1996) in Sweden have been reviewed. The ratio between number of fatal poisonings and prescription of defined daily dose/1000 inhabitants during a 12-month period (DDD) was determined. The highest ratio, 27, was attributed to unmixed preparations. The ratio for DXP + paracetamol-related deaths was 6.3, and for DXP + phenazone, 6.4, while the lowest ratio, 2, was found among the DXP + chlorzoxazone cases. The unmixed preparations, representing 26% of all DXP prescriptions during the study years, were implicated in 62% of the DXP fatalities, a considerable over-representation. Unmixed preparations, with their higher content of DXP, may be more attractive for many consumers because of their narcotic (euphoric) effects rather than for any analgetic superiority. Another possibility is that unmixed preparations may erroneously have been regarded as safer than when combined with paracetamol, as reports of poisoning with compounds containing DXP + paracetamol have been most frequently reported, probably due to their predominance on the market.

The prevalence of dextropropoxyphene in autopsy blood samples

The prevalence of dextroproxyphene (DXP) in the total medico-legal autopsy material in Sweden during 1992 to 1996 was examined. Simultaneous findings of paracetamol and alcohol in the blood were considered in the analyses. DXP in peripheral blood was found in 1782 (7.5%) of the 23,691 cases analysed during 1992-1996. The autopsy prevalence of DXP increased by 25% from 1992 to 1996. The mean blood DXP concentration was 1.62 micrograms/g (the blood level of DXP after a therapeutic dose is 0.05-0.75 microgram/g). The blood DXP level was < 0.75 microgram/g in 947 cases and > or = 0.75 microgram/g in 835 cases. The cases < 50 years of age had a significantly higher mean concentration (2.36 micrograms/g) than those > or = 50 years (1.04 micrograms/g). Paracetamol in the blood was found in 53% of the DXP cases (mean 75.0 micrograms/g; therapeutic level 2.5-25 micrograms/g) and alcohol in 43% (mean level 0.14%). According to the death certificates 54% (956) died from fatal poisoning. Among these, 74% (707) showed a blood DXP concentration > or = 0.75 microgram/g. Other Scandinavian countries, Denmark and Norway have reduced the rate of fatal DXP poisonings through government regulations for prescription. As the defined daily dose/1000 inhabitants during a 12-month period (DDD) of DXP preparations in Sweden (14.4 in 1996) is six times as high as in Denmark and nine times as high as in Norway, introduction of similar regulations in Sweden should be considered.

Analgesic use disorders among orthopedic and chronic pain patients at a rehabilitation clinic

Interviews were conducted with 265 orthopedic and chronic pain patients, using a structured diagnostic instrument (ADDIS/SUDDS) concerning their use of analgesics. Twenty-two percent of the patients met criteria for analgesic use disorders in accordance with DSM-III-R; 18.5% fulfilled DSM-IV criteria. Dextropropoxyphene was the most common analgesic prescribed and was used by 47% of the patients who met criteria for analgesic use disorders. It is concluded that patients with chronic pain using narcotic analgesics are at considerable risk of developing analgesic use disorders. Assessment of the use of analgesics should be offered to pain patients taking narcotic drugs.

Membrane toxicity of opioids measured by protozoan motility

The acute toxicity of some opioid drugs cannot solely be explained by a specific interaction with the opioid receptor. The anaesthetic-like membrane effect of 10 opioid agents and the antagonist naloxone was determined and correlated with their hydrophobicity. The inhibitory effect of drugs on protozoan motility was used as a measure of their membrane toxicity, measured by the reduction in swimming speed of Tetrahymena pyriformis using an image analysis system. Hydrophobicity was determined as the n-octanol/water partition coefficient, at pH 7.4, 37 degrees C. Opioid agents dose-dependently reduced the swimming speed of Tetrahymena pyriformis with a wide range of IC50 values. Some weak opioid agents were shown to have high protozoan immobilising potency comparable to quinidine, an agent with known membrane stabilising activity. Norpropoxyphene, the metabolite of dextropropoxyphene, with little affinity for the opioid receptor, also had a high potency. The inhibition of protozoan motility by these opioid agents was not antagonised by the opioid receptor antagonist naloxone; moreover an additive inhibitory action was demonstrated when opioid agents were combined with naloxone. The effect of opioid agents on protozoan motility was closely correlated with their partition coefficient but not with their known affinity for opioid receptors. These results suggest that opioid agents possess differing degrees of membrane depressant action independent from their interaction with the opioid receptor, and have a potential for causing depressant effects on excitable tissues.

Pharmacokinetics of dextropropoxyphene and nordextropropoxyphene in young and elderly volunteers after single and multiple dextropropoxyphene dosage

1. The pharmacokinetics of dextropropoxyphene (D) and nordextropropoxyphene (ND) have been studied in 12 healthy young (21-28 years) and 12 healthy elderly (70-79 years) male and female subjects. Each received 65 mg D and plasma D and ND concentrations were measured by h.p.l.c. with electrochemical detection for up to 7 days and again after 65 mg D, 3 times daily for 1 week. 2. There were no significant differences in median D and ND half-life, AUC, Cmax and tmax between the male and female subjects in either group. Within the groups the mean D half-life (h) was longer in the young after multiple dosing (mean +/- s.d.:13.2 +/- 5.2 and 23.7 +/- 11.3, P less than 0.05, paired t-test) but there were no other significant differences. 3. Between the groups, the median single and multiple dose D and ND half-lives were all significantly longer (P less than 0.02) and the median D AUC for both single and multiple doses was significantly higher (P less than 0.01 and P less than 0.05, respectively, Mann-Whitney U-tests) in the elderly. 4. There was no relation between multiple dose Cmax and other parameters such as single dose D half-life. However, across the groups D and ND half-lives after both single and multiple dosage correlated significantly with estimated creatinine clearance, the correlation being strongest with ND (r = -0.76 and -0.84, respectively).