Adverse cardiac manifestations following dextropropoxyphene overdose: can naloxone be helpful?

Overdose of Dologesic with a Fatal Outcome: A Case Report

Dologesic is a commonly prescribed analgesic in accident and emergency department. Yet report of overdose with this drug is not common. We report a case in which the patient developed cardiac arrest within an hour of ingestion. Dextropropoxyphene, a component of the drug Dologesic, used to be a common cause of fatalities after drug overdose in the seventies. It is highly toxic in overdose and therefore caution should be exercised when prescribing this drug.

Ventricular dysrhythmias associated with poisoning and drug overdose: a 10-year review of statewide poison control center data from California

BACKGROUND

Ventricular dysrhythmias are a serious consequence associated with drug overdose and chemical poisoning. The risk factors for the type of ventricular dysrhythmia and the outcomes by drug class are not well documented.

OBJECTIVE

The aim of this study was to determine the most common drugs and chemicals associated with ventricular dysrhythmias and their outcomes.

METHODS

We reviewed all human exposures reported to a statewide poison control system between 2002 and 2011 that had a documented ventricular dysrhythmia. Cases were differentiated into two groups by type of arrhythmia: (1) ventricular fibrillation and/or tachycardia (VT/VF); and (2) torsade de pointes (TdP).

RESULTS

Among the 300 potential cases identified, 148 cases met the inclusion criteria. Of these, 132 cases (89%) experienced an episode of VT or VF, while the remaining 16 cases (11%) had an episode of TdP. The most commonly involved therapeutic classes of drugs associated with VT/VF were antidepressants (33/132, 25%), stimulants (33/132, 25%), and diphenhydramine (16/132, 12.1%). Those associated with TdP were antidepressants (4/16, 25%), methadone (4/16, 25%), and antiarrhythmics (3/16, 18.75%). Drug exposures with the greatest risk of death in association with VT/VF were antidepressant exposure [odds ratio (OR) 1.71; 95% confidence interval (CI) 0.705-4.181] and antiarrhythmic exposure (OR 1.75; 95% CI 0.304-10.05), but neither association was statistically significant. Drug exposures with a statistically significant risk for TdP included methadone and antiarrhythmic drugs.

CONCLUSIONS

Antidepressants and stimulants were the most common drugs associated with ventricular dysrhythmias. Patients with suspected poisonings by medications with a high risk of ventricular dysrhythmia warrant prompt ECG monitoring.

Propoxyphene (dextropropoxyphene): a critical review of a weak opioid analgesic that should remain in antiquity

Propoxyphene (dextropropoxyphene) is a synthetic weak opioid introduced into the United States in 1957. It is most frequently prescribed in combination with acetaminophen and/or aspirin. After its ubiquitous introductory phase, it was soon discovered that this drug's iatrogenic events (cardiotoxicity, seizures, etc.) far outweighed any perceived therapeutic benefit. Propoxyphene analgesia was equated with that of merely acetaminophen or aspirin independently. The propoxyphenes euphorigenic component has created a problem in its prescribing. Use of this agent in the elderly should be avoided because of its complex pharmacokinetics and pharmacodynamics. The pharmacokinetics, pharmacodynamics, and pharmacology of this drug are discussed thoroughly in this article, including its arrhythmogenicity. Additional noncardiovascular pharmacotherapies that produce QTc prolongation or arrhythmogenicity are described. A list of the cytochrome P450 2D6 pharmacotherapies that will interact with propoxyphene is provided in the article. The use of this agent is highly discouraged. The rationale for this is discussed fully within this article. The toxicity of this drug is partially related to nor-propoxyphene a non-opioid cardiotoxic metabolite. The mere warnings of fatalities within the package insert should alert any cautious prescriber on the dangers of this agent and dampen its prescribing potential.

Trends in the pharmacology of opioids: implications for the pharmacotherapy of pain

Some 25 years ago, it was popular to write a figurative equation for drug treatment: Patient + drug --> effect. Clearly, this was too simplistic for the reliable pharmacotherapy of pain. The 'patient' with pain is a complex individual and the 'drug' is not the same in effect to every patient, regardless of being an opioid analgesic. Besides, the 'effect' needs specification: it really means an acceptable balance between therapeutic and side-effect--to that patient. These days, neural plasticity and neuromodulation associated with nociception are well-known. Psychological involvement in the physical domain of nociception is similarly well-known. Given these complexities, it is surprising that the pharmacological control of pain through the application of relatively simple analgesics can be so effective. Opioid analgesics have been administered by every possible route. Because the degree of invasion of the patient differs between routes, the balance between simplicity, aesthetic appeal, and efficacy of the various routes needs to be considered. The effectiveness of opioid analgesics depends in large measure on the application of the right agent, in the right dose, by the right route, at the right time for that patient. To assist in this task, researchers have produced patient-controlled analgesia and 'pharmacologically engineered' analgetic molecules to achieve receptor selectivity and pharmacokinetic predictability. Also, much relevant data concerning the time courses of analgetic drug (+/- metabolite) concentrations in the body and in the ways in which these properties are modified by different normal and pathophysiological variations have been gathered, and the philosophy of 'opioid rotation' has arisen to maintain therapeutic benefits when tolerance or metabolite-induced side-effects prevail. This essay discusses some of the trends in opioid pharmacotherapy over the past 25 years.

Electrophysiological mechanisms for the antiarrhythmic activities of naloxone on cardiac tissues

It has been reported that naloxone, an opioid antagonist, has antiarrhythmic activity in vivo. In Langendorff perfused rat hearts, we found that ischemia-reperfusion-induced ventricular tachyarrhythmia reverted to normal sinus rhythm after the treatment with naloxone (3 approximately 10 microM). The method of voltage and current clamp were used to study the underlying mechanism of its antiarrhythmic activity on isolated cardiac myocytes. In isolated rat ventricular and in guinea-pig and human atrial myocytes, naloxone prolonged the action potential duration reversibly. In rat ventricular myocytes, naloxone (1 approximately 30 microM) inhibited sodium current (I(Na)), transient outward potassium current (I(to)), and calcium current (I(Ca)). On the contrary, the addition of naloxone significantly increased inward rectifier potassium current (I(K1)). For the effect on I(Na), naloxone did not shift the inactivation curve of I(Na) but retarded the I(Na) recovery rate from inactivation state. Naloxone suppressed I(to) with a significant left-shift of the inactivation curve, however, the time course of I(to) recovery from inactivation was not affected. In guinea pig atrial myocytes, naloxone (10 microM) decreased the delayed rectifier K+ current (IK). These results show that naloxone exert various extent of inhibition on I(Na), I(to), IK and I(Ca). The prolongation of cardiac action potential is related to the inhibition of I(to) and IK. The antiarrhythmic activity of naloxone is more closely related to the inhibition of Na+ and K+ currents rather than the blockade of myocardial opioid receptors.

Antidotes: benefits and risks

The ability of naloxone and flumazenil to reverse serious toxicity due to their respective agonists is well known. Their adverse effects are minor and few but flumazenil administration may unmask seizures in poisoning with combinations of benzodiazepines and tricyclic antidepressants. The desferrioxamine challenge test is frequently falsely negative and should be abandoned. In addition to being cytoprotective, N-acetylcysteine has potent vasodilator and positive inotropic actions which may be partly responsible for its beneficial effect in late-presentation paracetamol overdosage with hepatic damage and failure.