Cyclic Antidepressant Overdoses

Psychiatric Medications and Hypertension

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of psychiatric medications that impact blood pressure in adult patients either as a direct side effect or indirectly, via negative metabolic impact or interactions with other medications. In addition, pertinent interactions between psychiatric medications and antihypertensive agents will be discussed.

RECENT FINDINGS

Although the novel intranasal antidepressant, esketamine, has been shown to increase blood pressure shortly after dosing, treatment with antihypertensive medications is not typically required. In addition, no increase in serious adverse cardiac events was reported with this medication. The negative metabolic impact of antipsychotic medications has been shown to occur within the first month of treatment and necessitates early monitoring. When compared with the general population with cardiovascular disease, mortality risk in patients with severe and persistent psychiatric illness is higher, and death occurs 10 years earlier. There are several psychiatric treatments that increase blood pressure directly as well as indirectly, via negative metabolic impact and drug/diet interactions. Fortunately, there are no absolute contraindications for use of any psychiatric medication in patients with pre-existing hypertension. Given data which suggests that patients diagnosed with more severe psychiatric disorders are known to receive inadequate medical care for hypertensive illness and experience increased mortality risk from cardiovascular disease, it is important for all physicians to be aware of the increased risk in this population and for both thorough assessment and treatment to occur.

Molecular determinants of Kv7.1/KCNE1 channel inhibition by amitriptyline

Amitriptyline (AMIT) is a compound widely prescribed for psychiatric and non-psychiatric conditions including depression, migraine, chronic pain, and anorexia. However, AMIT has been associated with risks of cardiac arrhythmia and sudden death since it can induce prolongation of the QT interval on the surface electrocardiogram and torsade de pointes ventricular arrhythmia. These complications have been attributed to the inhibition of the rapid delayed rectifier potassium current (I_Kr). The slow delayed rectifier potassium current (I_Ks) is the main repolarizing cardiac current when I_Kr is compromised and it has an important role in cardiac repolarization at fast heart rates induced by an elevated sympathetic tone. Therefore, we sought to characterize the effects of AMIT on Kv7.1/KCNE1 and homomeric Kv7.1 channels expressed in HEK-293H cells. Homomeric Kv7.1 and Kv7.1/KCNE1 channels were inhibited by AMIT in a concentration-dependent manner with IC50 values of 8.8 ± 2.1 μM and 2.5 ± 0.8 μM, respectively. This effect was voltage-independent for both homomeric Kv7.1 and Kv7.1/KCNE1 channels. Moreover, mutation of residues located on the P-loop and S6 domain along with molecular docking, suggest that T312, I337 and F340 are the most important molecular determinants for AMIT-Kv7.1 channel interaction. Our experimental findings and modeling suggest that AMIT preferentially blocks the open state of Kv7.1/KCNE1 channels by interacting with specific residues that were previously reported to be important for binding of other compounds, such as chromanol 293B and the benzodiazepine L7.

Lethal Tricyclic Antidepressant Overdose

Tricyclic antidepressant remains widely prescribed despite its dangerous cardiovascular and neurological effects in overdosed patients. We present a case of lethal dothiepin overdose and discuss the major complications and its management strategies.

Amitriptyline, clomipramine, and doxepin adsorption onto sodium polystyrene sulfonate

Purpose of the study

Comparative in vitro studies were carried out to determine the adsorption characteristics of 3 drugs on activated charcoal (AC) and sodium polystyrene sulfonate (SPS). Activated charcoal (AC) has been long used as gastric decontamination agent for tricyclic antidepressants (TCA).

Methods

Solutions containing drugs (amitriptyline, clomipramine, or doxepin) and variable amount of AC or SPS were incubated for 30 minutes.

Results

At pH 1.2 the adsorbent: drug mass ratio varied from 2 : 1 to 40 : 1 for AC, and from 0.4 : 1 to 8 : 1 for SPS. UV–VIS spectrophotometer was used for the determination of free drug concentrations. The qmax of amitriptyline was 0.055 mg/mg AC and 0.574 mg/mg SPS, qmax of clomipramine was 0.053 mg/mg AC and 0.572 mg/mg SPS, and qmax of doxepin was 0.045 mg/mg AC and 0.556 mg/mg SPS. The results of adsorption experiments with SPS revealed higher values for the qmax parameters in comparison with AC.

Conclusion

In vitro gastric decontamination experiments for antidepressant amitriptyline, clomipramine, and doxepin showed that SPS has higher qmax values than the corresponding experiments with AC. Therefore, we suggest SPS is a better gastric decontaminating agent for the management of acute TCA intoxication.

Antidepressant overdose-induced seizures

Treating patients with psychiatric problems can present numerous challenges for clinicians. The deliberate self-ingestion of antidepressants is one such challenge frequently encountered in hospitals throughout the United States. This review focuses on 1) the classes of antidepressants, their pharmacologic properties, and some of the proposed mechanism(s) for antidepressant overdose-induced seizures; 2) the evidence for seizures caused by antidepressants in overdose; 3) management strategies for patients who have intentionally or unintentionally overdosed on an antidepressant, or who have experienced an antidepressant overdose-induced seizure.

Antidepressant overdose-induced seizures

Antidepressants are the most commonly prescribed class of medications in the United States. The clinician should be mindful of the many antidepressants that can produce seizures following an accidental exposure or an overdose. A broader understanding of the seizure potential of antidepressants, combined with the ability to recognize individuals at risk for a seizure after an overdose, can aid clinicians in determining the need for inpatient monitoring, and help facilitate their treatment decisions.

Imipramine-Induced Cardiac Depression Is Responsible for the Increase in Intracellular Magnesium and the Activation of ERK 1/2 in Rats

Imipramine, an antidepressant drug, can cause potentially lethal cardiotoxic side effects including hypotension, ventricular tachycardia, and decreased cardiac output. This study investigated the mechanism responsible for imipramine-induced cardiac depression in rats. The left ventricular developed pressure (LVDP), velocity of the change in pressure (dP/dt), and heart rate (HR) accompanied with the total magnesium efflux ([Mg]e) were measured in Langendorff-perfused intact rats hearts. Intracellular ionized magnesium concentrations ([Mg2+] i) were measured using Mag-fura 2 AM in a single H9c2 cell. The activation of the extracellular signal-regulated kinases 1/2 (ERK 1/2) was analyzed by Western blot. Imipramine induced reversible decreases in LVDP, dP/dt, and HR, which were accompanied by increases in [Mg]e. Imipramine also induced activation of ERK 1/2 and increase in the [Mg2+] i, which was inhibited PD98059, ERK 1/2 inhibitor. These results suggest that imipramine-induced cardiac depression may be partly due to increases of [Mg2+]i that are accompanied by the activation of ERK 1/2 in rats.

Combined administration of the mixture of honokiol and magnolol and ginger oil evokes antidepressant-like synergism in rats

Magnolia bark combined with ginger rhizome is a common drug pair in traditional Chinese prescriptions for the treatment of depression. In the present study, we examined antidepressant-like effects of the mixture of honokiol and magnolol (HMM) from magnolia bark and essential oil from ginger rhizome (OGR) alone and in combination in chronic unpredictable mild stress (CUMS) of rats. Behavioral (sucrose intake, immobility time of forced swimming test) and biochemical parameters [serotonin (5-HT) in prefrontal cortex, hippocampus, and striatum, gastric mucosa cholecystokinin (CCK) and serum gastrin (GAS) levels] were simultaneously examined in the CUMS rats. 20 mg/kg HMM alone, but not OGR, significantly increased sucrose intake and reduced immobility time in the CUMS rats. Moreover, 20 mg/kg HMM and 14 mg/kg OGR in combination exhibited significant synergistic effects on sucrose intake increase and immobility time reduction in the CUMS rats. HMM elevated 5-HT levels in various brain regions, and OGR reduced gastric mucosa CCK and serum GAS levels in the CUMS rats. These results suggested that the synergistic antidepressant-like effects of compatibility of HMM with OGR might be mediated simultaneously by regulation of the serotonergic and gastroenteric system functions. These findings also provided a pharmacological basis for the clinical application of this drug pair of magnolia bark and ginger rhizome in traditional Chinese medicine.

Amitriptyline activates cardiac ryanodine channels and causes spontaneous sarcoplasmic reticulum calcium release

Patients taking amitriptyline (AMT) have an increased risk of sudden cardiac death, yet the mechanism for AMT's proarrhythmic effects remains incompletely understood. Here, we hypothesize that AMT activates cardiac ryanodine channels (RyR2), causing premature Ca(2+) release from the sarcoplasmic reticulum (SR), a mechanism identified by genetic studies as a cause of ventricular arrhythmias and sudden cardiac death. To test this hypothesis, we measured the effect of AMT on RyR2 channels from mice and sheep and on intact mouse cardiomyocytes loaded with the Ca(2+) fluorescent indicator Fura-2 acetoxymethyl ester. AMT induced trains of long channel openings (bursts) with 60 to 90% of normal conductance in RyR2 channels incorporated in lipid bilayers. The [AMT], voltage, and open probability (P(o)) dependencies of burst frequency and duration indicated that AMT binds primarily to open RyR2 channels. AMT also activated RyR2 channels isolated from transgenic mice lacking cardiac calsequestrin. Reducing RyR2 P(o) by increasing cytoplasmic [Mg(2+)] significantly inhibited the AMT effect on RyR2 channels. Consistent with the single RyR2 channel data, AMT increased the rate of spontaneous Ca(2+) releases and decreased the SR Ca(2+) content in intact cardiomyocytes. Intracellular [AMT] were approximately 5-fold higher than extracellular [AMT], explaining AMT's higher potency in cardiomyocytes at clinically relevant concentrations (0.5-3 muM) compared with its effect in lipid bilayers (5-10 muM). Increasing extracellular [Mg(2+)] attenuated the effect of AMT in intact myocytes. We conclude that the heretofore unrecognized activation of RyR2 channels and increased SR Ca(2+) leak may contribute to AMT's proarrhythmic and cardiotoxic effects, which may be counteracted by interventions that reduce RyR2 channel open probability.

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.

Are one or two dangerous? Tricyclic antidepressant exposure in toddlers

Tricyclic antidepressants (TCA), increasingly prescribed for multiple indications in children and adults, are responsible for many pediatric poisonings. Though the majority of TCA exposures in this age group remain asymptomatic, several reports in the English language literature reveal significant morbidity as well as fatalities in toddlers, primarily from imipramine and desipramine. These few cases indicate that doses of 10-20 mg/kg (one to two pills) have the potential for toxicity and fatalities. More recent studies have focused on the relative safety of small exposures suggesting that with doses less than 5 mg/kg the patient may be safely observed at home. Though further studies are necessary to determine the exact dosing that places the child at risk, the authors recommend a 6-h Emergency Department observation period for children who ingest more than 5 mg/kg of most TCAs, as clinical toxicity becomes evident within this time frame.

The effect of the nitric oxide synthesis inhibitor L-NAME on amitriptyline-induced hypotension in rats

OBJECTIVE

Hypotension induced by tricyclic antidepressants is multifactorial. Previous animal experiments suggest a contribution from nitric oxide production. Our study aimed to evaluate the role of nitric oxide in amitriptyline-induced hypotension using N-nitro-L-arginine methyl ester, a nitric oxide synthesis inhibitor, and 3-morpholino sydnonimine, a nitric oxide donor, in anesthetized rats.

METHODS

Amitriptyline intoxication was induced by the continuous infusion of amitriptyline 0.625 mg/kg/min throughout the experiment in anesthetized rats. Fifteen and 25 minutes after amitriptyline infusion began, two bolus doses of 10 mg/kg of N-nitro-L-arginine methyl ester (n = 8) or an equivalent volume of 5% dextrose solution (n = 8) was administered to each rat (Protocol 1). To investigate whether the effect of N-nitro-L-arginine methyl ester on blood pressure is counteracted by 3-morpholino sydnonimine, after the same protocol of amitriptyline infusion and 5 minutes after an N-nitro-L-arginine methyl ester bolus, a bolus of 3000 nmol/kg of 3-morpholino sydnonimine was administered (n = 8) to each rat (Protocol 2). To investigate the effect of N-nitro-L-arginine methyl ester on 3-morpholino sydnonimine induced hypotension, a group of rats received a continuous infusion of 0.54 mg/kg/h of 3-morpholino sydnonimine until 50% reduction was observed in mean arterial blood pressure followed by a bolus dose of 10 mg/kg of N-nitro-L-arginine methyl ester (n = 6) or 5% dextrose solution (n = 6) (Protocol 3). Outcome measures included mean arterial blood pressure, heart rate, and QRS duration in electrocardiogram. Student's t test and survival analysis were used for selected comparisons.

RESULTS

For all parameters, the treatment groups were similar at baseline and at postamitriptyline periods before therapy was rendered. Amitriptyline infusion significantly reduced mean arterial blood pressure by 50.8 +/- 2.2% and prolonged QRS by 23.9 +/- 7.2% after 15 minutes. In Protocol 1, N-nitro-L-arginine methyl ester significantly increased mean arterial blood pressure compared to dextrose-treated control animals within 30 minutes (77.9 +/- 8.5% vs. 49.7 +/- 5.0% mmHg, p < 0.01, 95% CI 57.1-98.7%). QRS duration progressively increased during the amitriptyline infusion; however, there was no significant difference in QRS width between N-nitro-L-arginine methyl ester and control groups at any time point. N-nitro-L-arginine methyl ester increased survival time compared to controls (33.4 +/- 4.1 vs. 19.9 +/- 2.7 minutes, p < 0.01, 95% CI 25.4-41.3) but did not affect mortality. In Protocol 2 of continuous infusion of amitriptyline, 3-morpholino sydnonimine counteracted the N-nitro-L-arginine methyl ester-induced increase in mean arterial blood pressure. In both protocols, heart rate decreased significantly during amitriptyline infusion but there was no difference between treatment and control groups. In Protocol 3, N-nitro-L-arginine methyl ester bolus reversed 3-morpholino sydnonimine-induced hypotension compared to dextrose bolus. (83.8 +/- 5.7% vs. 54.6 +/- 4.8%, p < 0.01, 95% CI 69.2-98.4).

CONCLUSION

N-nitro-L-arginine methyl ester is found to be effective in temporarily improving hypotension and prolonging survival time but does not affect overall mortality. Because this effect was antagonized by 3-morpholino sydnonimine, nitric oxide production appears to contribute to the pathophysiology of amitriptyline-induced hypotension.

Tricyclic antidepressants directly depress human myocardial mechanical function independent of effects on the conduction system

OBJECTIVES

To measure the effect of tricyclic antidepressant drugs (TCAs) on human myocardial contractility.

METHODS

Human atrial tissue was obtained during cardiac bypass surgery. The tissue was harvested, suspended in a Tyrode buffer at 37 degrees C, and perfused with a 95%/5% oxygen-carbon dioxide mixture. Developed force was continuously measured using a force transducer and recorded by computer. After an equilibration period, escalating doses of amitriptyline or desipramine were added to the bath. All strips were exposed to the following five concentrations of each drug: 0 (control) 0.4, 4, 40, and 400 microM. The results for each experiment were expressed as the difference between the developed force measured prior to the addition of each concentration of drug and the developed force measured after a 30-minute exposure to the drug.

RESULTS

Desipramine decreased the developed force by 27%, 49%, and 74% at concentrations of 0.4, 40, and 400 microM, respectively. Amitriptyline decreased the developed force by 38% at the 40-microM concentration and by 89% at the 400-microM concentration. Untreated strips retained 94% of baseline developed force at 150 minutes.

CONCLUSIONS

Tricyclic antidepressants depress human myocardial function in a dose-dependent fashion independent of the effects on the cardiac conduction system. While previous work has demonstrated the effect of therapies for the reversal of impaired cardiac conduction following TCA poisoning, to the best of the authors' knowledge, no reports have documented the effects of therapy on direct myocardial depression. Additional therapies targeted at reversing the direct cardiodepressive effects of TCA may improve outcome following TCA poisoning.

Plasma alkalinization for tricyclic antidepressant toxicity: a systematic review

OBJECTIVE

To review the evidence that plasma alkalinization improves the outcome in tricyclic antidepressant toxicity.

METHODS

Medline search from 1966 to October 2000 (articles in all languages were included) and examination of bibliographies. Published papers including animal studies, in vitro studies, human case reports, case series and retrospective studies were reviewed.

RESULTS

Our search identified 115 publications, all of which were retrieved. Human studies included eight case reports, four case series, one controlled study and two retrospective chart reviews. No randomized controlled human trials were found. Twelve animal studies were identified that investigated pH manipulation or saline load and their effects on physiological parameters in tricyclic antidepressant toxicity.

CONCLUSIONS

The practice of alkalinization for tricyclic antidepressant toxicity is based on animal studies, case reports and opinion. The mechanism of action appears to be multifaceted and may vary between different tricyclic antidepressants. Significant interspecies variation makes extrapolation from animal studies to humans difficult. Alkalinization therapy appears reasonable in patients with compromising dysrhythmias and shock when supportive interventions have been ineffective; however, the available evidence does not support prophylactic alkalinization in the absence of life-threatening cardiovascular toxicity.

Selected tricyclic antidepressant ingestions involving children 6 years old or less

OBJECTIVE

According to the annual report of the American Association of Poison Control Centers, tricyclic antidepressant (TCA) ingestions accounted for 15,708 exposures in 1998, of which 70% (all age groups) were treated at health care facilities (HCFs), with an estimated 2,022 children less than 6 years of age exposed. The study objective was to evaluate the manifestations, referral patterns, HCF management, and medical outcomes in pediatric patients 6 years old or less with TCA ingestions reported to a regional poison control center.

METHODS

All TCA (amitriptyline, clomipramine, desipramine, doxepin, imipramine, nortriptyline) ingestions from January 1, 1993, to December 31, 1997, involving patients aged 6 years or less managed by the poison control center were evaluated for dose, symptoms, treatments, disposition, and outcome.

RESULTS

Forty-four of 48 patients (92%) were asymptomatic. All were single-drug exposures. Forty-three patients (90%) ingested a TCA dose that was less than the normally prescribed pediatric dose (5 mg/kg). Of the five children ingesting >5 mg/kg (range 5-9.4 mg/kg), only one (5.3 mg/kg) was mildly symptomatic (drowsy) prior to admission. Thirty-one of the 48 (65%) were sent to the emergency department (dose range 0.59-9.4 mg/kg). Fourteen of the 31 were admitted for 12-24-hour observation and none subsequently developed symptoms. Twenty-three (74%) received activated charcoal (AC). There was no difference in outcome between the children who did and did not receive AC.

CONCLUSIONS

No case of significant toxicity occurred in the children who experienced unintentional TCA ingestions in this study population. None of the children in the study had toxicity at doses <5 mg/kg. Further study is necessary to develop clinical guidelines for the appropriate referral of unintentional ingestions of TCA involving children.

Amitriptyline-induced loss of tight junction integrity in a human endothelial--smooth muscle cell bi-layer model

Tricyclic antidepressants can, when taken in overdose, cause serious pulmonary failure such as the adult respiratory distress syndrome (ARDS). In this study we have examined the effects of some tricyclic antidepressants (amitriptyline, imipramine, nortriptyline and desipramine) on the viability and morphology of human endothelial and smooth muscle cells derived from umbilical cord. Effects of amitriptyline on endothelial cell fluidity, as well as permeability changes to an endothelial-smooth muscle cell bi-layer, were also studied. The tricyclic antidepressants induced acute, sub-lethal toxicity in both cell types above 100 microM as assessed by the MTT reduction assay. Morphological changes were also observed at these concentrations. Such changes were, however, absent at 33 microM and below. Amitriptyline did, however, cause a concentration-dependent fall in the electrical resistance of an endothelial-smooth muscle cell bi-layer, with significant effects already evident at 33 microM. All of these observed effects were fairly rapid and appeared within 5-15 min of exposure. The rapidity of these permeabilisation effects suggests potential membrane perturbations, since tricyclic antidepressants are lipophilic molecules with affinity for cell membranes. However, fluorescence anisotropy measurements showed no significant difference in membrane fluidity between amitriptyline-treated and control endothelial cells. Collectively, these data point to specific mechanisms of action of amitriptyline, and probably also the other tricyclic antidepressants studied, on endothelial permeability, which is a hallmark of ARDS. The data suggest that increased endothelial permeability could be due to impaired tight junction function.

Cocaine-induced wide complex dysrhythmia

Cocaine is a local anesthetic with the potential to induce dysrhythmia due to direct myocardial sodium channel antagonism similar to class I antidysrhythmic drugs. The hallmark of myocardial sodium channel poisoning is wide complex dysrhythmia, and the current accepted treatment is intravenous bicarbonate. Wide complex dysrhythmio due to cocaine in the absence of myocardial infarction is rare, and optimum management is undefined. We report three cases of acute cocaine intoxicating during which patients developed wide complex dysrhythmia consistent with sodium channel poisoning. In one case, wide complex tachycardia resolved without direct treatment. In the other cases, wide complex dysrhythmia resolved following intravenous bicarbonate therapy directed at reversing sodium channel blockade.