Low-dose naloxone does not improve morphine-induced nausea, vomiting, or pruritus

Use of Prophylactic Ondansetron with Intravenous Opioids in Emergency Department Patients: A Prospective Observational Pilot Study

BACKGROUND

The current literature suggests that the prophylactic use of antiemetics is ineffective at preventing nausea or vomiting caused by opioids in the emergency department (ED). While there is no data evaluating ondansetron's efficacy for preventing opioid-induced nausea and vomiting, this practice remains common despite a lack of supporting evidence.

OBJECTIVES

This study aimed to identify if prophylactic ondansetron administered with intravenous (IV) opioids prevents opioid-induced nausea or vomiting.

METHODS

This prospective observational study was conducted in the ED at two academic medical institutions. Patients were eligible for enrollment if they were prescribed an IV opioid with or without IV ondansetron and absence of baseline nausea. Patients' level of nausea was evaluated at baseline, 5 min, and 30 min after an IV opioid was administered and then observed for 2 hours.

RESULTS

One hundred thirty-three patients were enrolled, with 90% of patients presenting with a chief complaint of pain. Sixty-four (48.1%) patients received an IV opioid alone and 69 (51.9%) patients received both IV ondansetron and an IV opioid. Twenty-three (17.3%) patients developed nausea caused by opioid administration. One (0.75%) patient had an emetic event and 3 (2.3%) patients required rescue antiemetics during their observation period. Rate of nausea was similar between treatment groups 5 min after the opioid was administered (p = 0.153). There was no statistical difference in emesis, rescue medication requirements, or nausea severity between treatment groups.

CONCLUSION

Our trial found that ondansetron did not appear to be effective at preventing opioid-induced nausea or vomiting. These findings and previous literature suggest prophylactic ondansetron should not be given to ED patients who are receiving IV opioids.

Predicting morphine related side effects in the ED: An international cohort study

STUDY OBJECTIVES

Morphine is the reference treatment for severe acute pain in an emergency department. The purpose of this study was to describe and analyse opioid-related ADRs (adverse drug reactions) in a large cohort of emergency department patients, and to identify predictive factors for those ADRs.

METHODS

In this prospective, observational, pharmaco-epidemiological international cohort study, all patients aged 18years or older who were treated with morphine were enrolled. The study was done in 23 emergency departments in the US and France. Baseline numerical rating scale score and initial and total doses of morphine titration were recorded. Logistic regression analysis was used to study the effects of demographic, clinical and medical history covariates on the occurrence of opioid-induced ADRs within 6h after treatment.

RESULTS

A total of 1128 patients were included over 10months. Median baseline initial pain scores were 8/10 (7-10) versus 3/10 (1-4) after morphine administration. Median titration duration was 10min (IQR, 1-30). The occurrence of opioid-induced ADRs was 25% and 2% were serious. Patients experienced mainly nausea and drowsiness. Medical history of travel sickness (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.01-2.86) and history of nausea or vomiting post morphine (OR, 3.86; 95% CI, 2.29-6.51) were independent predictors of morphine related ADRs.

CONCLUSION

Serious morphine related ADRs are rare and unpredictable. Prophylactic antiemetic therapy could be proposed to patients with history of travel sickness and history of nausea or vomiting in a postoperative setting or after morphine administration.

Measuring nausea in emergency department patients via the use of exploratory factor analysis

OBJECTIVES

The objective was to evaluate the applicability of a previously studied multifactorial nausea scale in the emergency department (ED) setting via exploratory factor analysis (EFA).

METHODS

Two studies evaluated the validity and factor structure of 18 nausea descriptors scored on 11-point Likert scales. Trained research volunteers administered the scale to 83 men and 123 women in the first sample and to 100 men and 230 women in the second sample. All patients were assessed at enrollment and again at 90 minutes to detect changes in symptom severity. An EFA in the first study used a maximum likelihood estimation method with a principal factor analysis. The second study narrowed the descriptors and evaluated the factor structure with a confirmatory factor analysis (CFA).

RESULTS

Two factors were retained in the solution; one contained five items with descriptors of physical symptoms, and a second contained five items with psychological symptoms. CFA determined that the two five-item scales were stable and reliable measures of patient nausea experience.

CONCLUSIONS

The scales measure both physical and psychological symptoms of nausea, indicating that the experience is multidimensional.

[Opioid-induced pruritus. Mechanisms and treatment regimens]

Substantial progress has been achieved in recent years in research on the interaction between pain and pruritus. Over and above the known inhibition of pruritus by painful stimuli (e.g. scratching), a foundation for the explanation of opioid-induced pruritus was laid through the discovery of pruritus-specific neuronal processing channels. Although traditionally the degranulating effect of opioids on mast cells was assumed to be the essential mechanism, it is now clear that opioids can also induce itching at the spinal level. Neurons of the dorsal horn of the pain system inhibit spinal itch neurons. If this inhibition is weakened by opioids, the disinhibited itch neurons become active and mediate itching, without stimulation of the primary afferent peripheral nerves. Spinal triggering of itching is observed in particular by activation of mu-opioid receptors (mu-OR), while kappa-OR surprisingly suppress itch. The therapeutic implications of this interaction will be described.

Pilot study of continuous co-infusion of morphine and naloxone in children with sickle cell pain crisis

Patients with sickle cell disease experience painful crises that often require hospitalization for a continuous infusion of morphine that may cause significant pruritus. We conducted a pilot study to determine the feasibility of simultaneous continuous co-infusion of naloxone with morphine, test novel assessment instruments for pruritus, and explore whether pruritus could be reduced while maintaining effective analgesia. Patients with sickle cell disease and painful crisis requiring continuous infusion morphine received continuous co-infusion of naloxone at 0.25 (low dose) or 1.0 mcg/kg x hr (high dose). Pain scores were obtained using the FACES scale and a 100-mm visual analog scale (VAS). Itching was quantified by a modified VAS score. Evaluable data were obtained on 16 patients. Simultaneous co-infusion of naloxone and morphine was feasible, did not seem to reduce the analgesic efficacy of morphine, and was associated with no adverse effects. The high dose group reported a lower median "VAS worst itch" score than the low dose group (4.8 vs. 7.3, P = 0.08). Simultaneous continuous infusion of naloxone with morphine in pediatric patients with sickle cell disease and pain crisis was feasible and well tolerated. A quantitative pruritus score allowed us to systematically measure pruritus. Further evaluation by randomized, placebo-controlled study of 1 mcg/kg x hr naloxone in this setting is required.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).