Oral morphine overdose in a cancer patient antagonized by prolonged naloxone infusion

PBPK-PD model for predicting morphine pharmacokinetics, CNS effects and naloxone antagonism in humans

Morphine and morphine-6-glucuronide (M6G) produce central nervous system (CNS) effects by activating mu-opioid receptors, while naloxone is used mainly for the reversal of opioid overdose, specifically for the fatal complication of respiratory depression, but also for alleviating opioid-induced side effects. In this study we developed a physiologically-based pharmacokinetic-pharmacodynamic (PBPK-PD) model to simultaneously predict pharmacokinetics and CNS effects (miosis, respiratory depression and analgesia) of morphine as well as antagonistic effects of naloxone against morphine. The pharmacokinetic and pharmacodynamic parameters were obtained from in vitro data, in silico, or animals. Pharmacokinetic and pharmacodynamic simulations were conducted using 39 and 36 clinical reports, respectively. The pharmacokinetics of morphine and M6G following oral or intravenous administration were simulated, and the PBPK-PD model was validated using clinical observations. The Emax model correlated CNS effects with free concentrations of morphine and M6G in brain parenchyma. The predicted CNS effects were compared with observations. Most clinical observations fell within the 5th-95th percentiles of simulations based on 1000 virtual individuals. Most of the simulated area under the concentration-time curve or peak concentrations also fell within 0.5-2-fold of observations. The contribution of morphine to CNS effects following intravenous or oral administration was larger than that of M6G. Pharmacokinetics and antagonistic effects of naloxone on CNS effects were also successfully predicted using the developed PBPK-PD model. In conclusion, the pharmacokinetics and pharmacodynamics of morphine and M6G, antagonistic effects of naloxone against morphine-induced CNS effects may be successfully predicted using the developed PBPK-PD model based on the parameters derived from in vitro, in silico, or animal studies.

Clinically Significant Drug-Drug Interactions Involving Medications Used for Symptom Control in Patients With Advanced Malignant Disease: A Systematic Review

CONTEXT

Most patients with advanced malignant disease need to take several drugs to control symptoms. This treatment raises risks of serious adverse effects and drug-drug interactions (DDIs).

OBJECTIVES

To identify studies reporting clinically significant DDIs involving medications used for symptom control, other than opioids used for pain management, in adult patients with advanced malignant disease.

METHODS

Systematic review with searches in Embase, MEDLINE, and the Cochrane Central Register of Controlled Trials, from the start of the databases (Embase from 1980) through June 21, 2018. In addition, reference lists of relevant full-text articles were hand-searched.

RESULTS

Of 9699 retrieved citations, 462 were considered potentially eligible. After full-text reading, 29 were included in the final analysis, together with 13 articles from reference lists. The 42 included publications were case reports, letters to the Editor, and one retrospective study. Drugs most often involved were antiepileptics, antidepressants, corticosteroids, and nonopioid analgesics. Clinical manifestations of identified DDIs included sedation, respiratory depression, serotonin syndrome, neuroleptic malignant syndrome, delirium, seizures, ataxia, liver and kidney failure, bleeding, cardiac arrhythmias, rhabdomyolysis, and others. The most common mechanisms eliciting DDIs were alteration of CYP450-dependent metabolism and overstimulation of serotonin receptors in the central nervous system.

CONCLUSION

Drugs used for symptom control in patients with advanced cancer may cause serious DDIs. Although there is limited evidence for the risk of clinically significant DDIs, physicians treating patients with cancer should try to limit polypharmacy, avoid drug combinations with a high risk of DDIs, and closely monitor patients for adverse drug reactions.

Clinically significant drug-drug interactions involving opioid analgesics used for pain treatment in patients with cancer: a systematic review

BACKGROUND

Opioids are the most frequently used drugs to treat pain in cancer patients. In some patients, however, opioids can cause adverse effects and drug-drug interactions. No advice concerning the combination of opioids and other drugs is given in the current European guidelines.

OBJECTIVE

To identify studies that report clinically significant drug-drug interactions involving opioids used for pain treatment in adult cancer patients.

DESIGN AND DATA SOURCES

Systematic review with searches in Embase, MEDLINE, and Cochrane Central Register of Controlled Trials from the start of the databases (Embase from 1980) through January 2014. In addition, reference lists of relevant full-text papers were hand-searched.

RESULTS

Of 901 retrieved papers, 112 were considered as potentially eligible. After full-text reading, 17 were included in the final analysis, together with 15 papers identified through hand-searching of reference lists. All of the 32 included publications were case reports or case series. Clinical manifestations of drug-drug interactions involving opioids were grouped as follows: 1) sedation and respiratory depression, 2) other central nervous system symptoms, 3) impairment of pain control and/or opioid withdrawal, and 4) other symptoms. The most common mechanisms eliciting drug-drug interactions were alteration of opioid metabolism by inhibiting the activity of cytochrome P450 3A4 and pharmacodynamic interactions due to the combined effect on opioid, dopaminergic, cholinergic, and serotonergic activity in the central nervous system.

CONCLUSION

Evidence for drug-drug interactions associated with opioids used for pain treatment in cancer patients is very limited. Still, the cases identified in this systematic review give some important suggestions for clinical practice. Physicians prescribing opioids should recognize the risk of drug-drug interactions and if possible avoid polypharmacy.

Use of naloxone for reversal of life-threatening opioid toxicity in cancer-related pain

Objective

To review the emergency-based approach to opioid toxicity reversal in cancer-related pain patients.

Data source

A MEDLINE and PubMed search was conducted (1966 to May 2014) using the terms opioids, cancer, naloxone, respiratory depression, morphine, morphine derivatives, emergency, and anaphylaxis.

Methods of study selection

English articles in human subjects identified from the MEDLINE and PubMed search were evaluated. Citations were excluded if they addressed acute overdoses, non-cancer pain, and/or acute, non-chronic pain.

Data extraction and synthesis

Pain is a common occurrence in the oncology population. Although toxicity from opioids is common, life-threatening toxicities are not. The use of naloxone in this particular patient population occurs frequently for any perceived opioid-related effect and can be detrimental to the oncology patient’s care and quality of life. Difficulties exist when attempting to separate opioid toxicity from disease progression or metastases and, therefore, a thorough history is needed prior to complete opioid reversal in this population. Severity of the opioid intoxication should dictate reversal strategy. Dosing strategies that take into account both the treatment of the opioid-related effects as well as the negative effects reversal will have on the patient are offered. We also review the pre-hospital setting and identified the need for protocols that not only take the patient’s symptoms into account, but also the patient’s cancer history.

Conclusion

Opioid reversal protocols should be developed by a multi-disciplinary team. Each protocol should differentiate those toxicities which are life-threatening and require complete opioid reversal with toxicities that require small aliquots of naloxone to mitigate the presenting symptoms.

[Limits of pain treatment: medical and judicial aspects]

Medical principles of pain treatment are generally in line with the judicial principles. To relieve pain is one of the fundamentals of medicine and this has also been acknowledged by the Federal Court in Germany. It is criminal bodily harm, when a physician denies a possible pain treatment. Whereas courts clearly see an obligation to basic and continuing education in pain diagnosis and therapy, pain is still not represented in the German licensing regulations for physicians. Only palliative medicine has been added to the obligatory curriculum. Very similar pain is not mandatory in many clinical disciplines leaving physicians without the needed knowledge to treat pain. The need for interdisciplinary treatment is not yet acknowledged sufficiently, although meanwhile chronic pain is regarded as a bio-psycho-social illness.Since 2009 the advance directive is regulated by law. However, still many physicians are unaware that not only the position of the patient but also of the relatives have been strengthened. In 2010 the Federal Court has pronounced a judgment allowing "passive euthanasia" in certain conditions but prohibiting any active handling even in line with the patient's will. This is also in line with the European Human Rights Convention. The judicial unpunished assisted suicide has provoked an ethical discussion within the medical profession. However, what is not illegal is not automatically accepted as ethical handling for physicians. Palliative medicine is at least one alternative in this discussion.