Diphenhydramine overdose mimicking serotonin syndrome

A Qualitative Analysis of First-Hand Accounts of Diphenhydramine Misuse Available on YouTube

Deliriants are the least studied class of hallucinogens and display noticeable subjective effects, including dysphoria, hallucinations, and substantial alterations in thought. High doses of diphenhydramine (DPH), an over-the-counter antihistamine medication, can produce deliriant effects due to secondary anticholinergic activity. We sought to characterize the subjective experiences produced by DPH misuse to better understand deliriants more broadly and the context under which DPH misuse occurs. To conduct our analysis, 32 first-hand accounts of DPH misuse publicly available in YouTube videos were analyzed using inductive thematic analysis. Video makers discussed alterations in most sensory modalities, confusion, and a tendency for strongly unpleasant experiences. Occasionally, video makers reported positive effects, although these were rare and often overshadowed by negative aspects of the experience. Video makers frequently warned against misusing DPH, and these individuals occasionally reported adverse post-acute effects. Despite the prevalence of adverse experiences, patterns of repeated misuse were sometimes discussed. Motives for misusing DPH, when mentioned, included accessibility, affordability, and legality. Overall, findings suggest DPH misuse can produce substantial psychoactive effects that are often distressing and share some phenomenological overlap with experiences produced by psychosis.

Efficacy of lipid emulsion therapy in treating cardiotoxicity from diphenhydramine ingestion: a review and analysis of case reports

INTRODUCTION

Lipid emulsion therapy (LET) has been most thoroughly studied to reverse local anesthetic systemic toxicity (LAST). Case reports suggest that LET can successfully rescue cardiovascular collapse from bupropion, amitriptyline, and propranolol. The efficacy of LET against refractory hypotension and dysrhythmias from diphenhydramine, a commonly ingested lipophilic cardiotoxic agent, is less well described.

OBJECTIVE

Summarize the evidence that LET rescues cardiac ion channel blockade (QRS, QTc widening) or hypotension attributable to diphenhydramine overdose.

METHODS

We searched MEDLINE, EMBASE, and Google Scholar for English-language full-length case reports of diphenhydramine (DPH) intoxication in patients 17 years of age or older. We extracted data with a PRISMA-compliant protocol, dividing the case reports into two groups, one that received LET and one that did not. We performed a pooled analysis to compare the change in mean arterial pressure (MAP), QRS duration, and QTc duration between the two groups.

RESULTS

We identified 23 reports (25 patients). Lipid emulsion therapy (LET) was used in 6 cases because the patient suffered from hypotension refractory to traditional resuscitation. Those who received LET and those who did not were comparable in age, gender, amount ingested, and frequency of seizures. The mean arterial pressure (MAP) decreased by 4.5 ± 11.5 mm Hg in those who did not receive LET compared to an increase in MAP 37 ± 17.5 mm Hg in those who did receive LET. The QRS narrowed by 29 ± 33.9 ms (no LET group) vs 68 ± 49.5 ms (LET group) and QTc by 168.5 ± 126.75 ms (no LET group) vs 134 ± 88 ms (LET group). All values are expressed as median ± interquartile range. One out of the 6 patients who received LET died after withdrawal of care. In the group that did not receive LET 4 out of 19 died and 3 had no outcome reported.

DISCUSSION

LET may improve MAP in patients with hypotension refractory to vasopressors due to diphenhydramine toxicity. We found no significant effect of LET on QRS or QTc duration. These results are limited by a small sample size, reporting bias of case reports, incomplete data, and heterogeneity.

CONCLUSION

An analysis of pooled case reports suggests that LET may rescue hypotension when other methods have failed in patients with hypotension attributable to diphenhydramine overdose.

Striatal histamine mechanism in the pathogenesis of restless legs syndrome

STUDY OBJECTIVES

Restless legs syndrome (RLS) has been hypothesized to be generated by abnormal striatal dopamine transmission. Dopaminergic drugs are effective for the treatment of RLS. However, long-term use of dopaminergic drugs causes adverse effects. We used iron-deficient (ID) and iron-replacement (IR) rats to address the neuropathology of RLS and to determine if a histamine H3 receptor (H3R) antagonist might be a useful treatment. Histamine H3R antagonists have been shown to decrease motor activity.

METHODS

Control and ID rats were surgically implanted with electrodes for polysomnographic recording. After 3 days of baseline polysomnographic recordings, rats were systemically injected with the H3R agonist, α-methylhistamine, and antagonist, thioperamide. Recordings were continued after drug injection. Striatal H3R levels from control, ID, and IR rats were determined by western blots. Blood from control, ID, and IR rats was collected for the measurement of hematocrit levels.

RESULTS

α-Methylhistamine and thioperamide increased and decreased motor activity, respectively, in control rats. In ID rats, α-methylhistamine had no effect on motor activity, whereas thioperamide decreased periodic leg movement (PLM) in sleep. Sleep-wake states were not significantly altered under any conditions. Striatal H3R levels were highest in ID rats, moderate to low in IR rats, and lowest in control rats. Striatal H3R levels were also found to positively and negatively correlate with PLM in sleep and hematocrit levels, respectively.

CONCLUSIONS

A striatal histamine mechanism may be involved in ID anemia-induced RLS. Histamine H3R antagonists may be useful for the treatment of RLS.

Management of severe arterial hypertension associated with serotonin syndrome: a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary.

Reduced anxiety is associated with the accumulation of six serotonin reuptake inhibitors in wastewater treatment effluent exposed goldfish Carassius auratus

Pharmaceuticals and personal care products (PPCPs) have been found in wastewater treatment plant (WWTP) effluents and their recipient watersheds. To assess the potential of WWTP effluents to alter fish behaviour, we caged male goldfish (Carassius auratus) for 21-days at three sites along a contamination gradient downstream from a WWTP which discharges into Cootes Paradise Marsh, on the western tip of Lake Ontario. We also included a fourth caging site as an external reference site within Lake Ontario at the Jordan Harbour Conservation Area. We then measured concentrations of PPCPs and monoamine neurotransmitters in caged goldfish plasma, and conducted behavioural assays measuring activity, startle response, and feeding. We detected fifteen different PPCPs in goldfish plasma including six serotonin reuptake inhibitors (amitriptyline, citalopram, fluoxetine/norfluoxetine, sertraline, venlafaxine, and diphenhydramine). Plasma concentrations of serotonin were significantly greater in plasma of fish caged closer to the WWTP effluent outfall site. The fish caged near and downstream of the WWTP effluent were bolder, more exploratory, and more active overall than fish caged at the reference site. Taken together, our results suggest that fish downstream of WWTPs are accumulating PPCPs at levels sufficient to alter neurotransmitter concentrations and to also impair ecologically-relevant behaviours.

Diphenhydramine exposure in dogs: 621 cases (2008-2013)

OBJECTIVE To characterize the signalment, dose response, and clinical signs of diphenhydramine toxicosis in dogs. DESIGN Retrospective case series. ANIMALS 621 dogs with diphenhydramine exposure. PROCEDURES The electronic medical record database for an animal poison control center was reviewed from January 2008 through December 2013 to identify dogs that had ingested or been injected with diphenhydramine. Information extracted from the records and evaluated included the signalment, clinical signs observed, and estimated exposure dose of diphenhydramine. Clinical signs were categorized as none, mild, moderate, and severe. RESULTS The mean ± SEM age of dogs was 3.6 ± 0.1 years (range, 0.1 to 16 years). Diphenhydramine exposure was by ingestion for 581 (93.6%) dogs and injection for 40 (6.4%) dogs. Only 146 (23.5%) dogs developed ≥ 1 clinical signs of toxicosis, the most common of which were associated with the nervous (lethargy, hyperactivity, agitation, hyperthermia, ataxia, tremors, and fasciculations) or cardiovascular (tachycardia) systems, and 3 dogs died. Although the presence and extent of clinical signs varied greatly among dogs, the exposure dose of diphenhydramine was positively associated with the severity of clinical signs in a dose-dependent manner regardless of the route of exposure (ingestion or injection). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that dogs exposed to diphenhydramine developed clinical signs of toxicosis fairly infrequently, and those clinical signs were generally mild and primarily affected the neurologic and cardiovascular systems. Supportive treatment for diphenhydramine toxicosis should be administered on the basis of the clinical signs observed.

Serotonergic or Anticholinergic Toxidrome: Case Report of a 9-Year-Old Girl

OBJECTIVE

The aim of this study was to report an acute onset of symptoms erroneously attributed to serotonin syndrome in a child who had been given both anticholinergic and serotonergic agents.

CASE SUMMARY

A 9-year-old girl with chronic anxiety and gastrointestinal problems was prescribed oral sertraline 6.25 mg daily, as well as hyoscyamine, ondansetron, montelukast, and a course of nitazoxanide. She was also routinely given diphenhydramine and omeprazole. Three days after increasing sertraline to 12.5 mg, she presented to the emergency department with altered mental status, hallucinations, mydriasis, tachycardia, and pyrexia. She was admitted to the pediatric intensive care unit and subsequently treated unsuccessfully for serotonin syndrome, with blurred vision and clonus persisting at discharge 4 days after admittance. Upon follow-up with her outpatient clinic, all anticholinergic agents were discontinued, and symptoms slowly resolved.

CONCLUSIONS

This case illustrates the importance of differential diagnosis between toxidromes and how clinical presentation can be altered by preexisting conditions as well as the use of medications that affect multiple neurotransmitter systems.