Benzonatate Safety and Effectiveness: A Systematic Review of the Literature

OBJECTIVE

To review the available literature regarding the treatment effects and efficacy of benzonatate needed to better inform patients, providers, and regulators evaluating its role in modern medical therapies.

DATA SOURCES

Comprehensive literature searches were conducted in PubMed, Embase (Elsevier), Cochrane Library, and Scopus for original research articles evaluating the effectiveness, tolerability, and safety profile of benzonatate from January 1956 through August 2022.

STUDY SELECTION AND DATA EXTRACTION

The identified studies were screened for relevance and then assessed for inclusion through a full-text review, data extraction, and quality assessment by multiple reviewers using the online software Covidence.

DATA SYNTHESIS

The selection process resulted in 37 articles consisting of 21 cohort studies, 5 experimental studies, and 11 case studies and series. Initial clinical studies exploring potential therapeutic benefits collected data from very small populations and limited clinical settings. Safety is primarily assessed in terms of toxicity due to overdose or inappropriate use. Quality assessment raised concerns for high degrees of biases primarily related to the limited sample size, data collection, generalizability, and study design.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review reveals substantial limitations within existing evidence pertaining to the safety and clinical effectiveness of benzonatate and thus, a need for large observational studies or randomized trials to better characterize its role and value in modern medical practice.

CONCLUSIONS

Rising safety concerns should bring closer scrutiny upon the prescription of benzonatate whose approval is founded upon evidence that would not stand up to current regulatory review.

Benzonatate Exposure Trends and Adverse Events

BACKGROUND AND OBJECTIVES

Adverse events (AE), including death, occur in children with benzonatate use. This study aims to understand recent trends in benzonatate exposure and clinical consequences in pediatric patients.

METHODS

This retrospective analysis of data from IQVIA pharmacy drug dispensing, National Poison Data System, National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance Project, FDA Adverse Event Reporting System, and the medical literature evaluated exposure trends and medication-related AEs with benzonatate. Trends for comparator narcotic and nonnarcotic antitussive medications were analyzed where possible for context.

RESULTS

During the study period, pediatric benzonatate prescription utilization increased but remained low compared with pediatric utilization of dextromethorphan-containing prescription antitussive medications. Among the 4689 pediatric benzonatate exposure cases reported to US poison control centers from 2010 to 2018, 3727 cases (80%) were for single-substance exposures. Of these, 3590 cases (77%) were unintentional exposures and most involved children 0 to 5 years old (2718 cases, 83%). Cases involving intentional benzonatate exposure increased among children 10 to 16 years old with a more pronounced increase for multiple-substance exposures. Most benzonatate cases involving misuse or abuse were for children 10 to 16 years old (59 cases, 61%). The proportion of cases with serious adverse effects was low. There were few cases annually of serious AEs with benzonatate in children.

CONCLUSIONS

There were rising patterns of unintentional ingestion of benzonatate in children 0 to 5 years old and intentional benzonatate ingestion in children 10 to 16 years old. Rational prescribing and improved provider and caregiver awareness of benzonatate toxic effects may reduce risks associated with benzonatate exposure.

Benzonatate Overdose Presenting as Cardiac Arrest with Rapidly Narrowing QRS Interval

INTRODUCTION

Benzonatate is a local anesthetic-like sodium channel antagonist that is widely prescribed as an antitussive. While it may be reasonable to assume that patients would present with a prolonged QRS interval following benzonatate overdose, the published literature does not support this. We report a case of a patient presenting following a benzonatate overdose with a prolonged QRS on her initial electrocardiograph (ECG) rhythm strip with rapid normalization of QRS duration.

CASE REPORT

A 14-year-old girl presented in cardiac arrest following a benzonatate overdose. The patient was found in cardiac arrest within minutes of last being known well. Bystanders immediately provided cardiopulmonary resuscitation (CPR), and she was in asystole on emergency medical services (EMS) arrival. Return of spontaneous circulation (ROSC) was obtained following administration of intraosseous epinephrine and naloxone. EMS obtained an ECG rhythm strip following ROSC demonstrating a sinus rhythm with a QRS duration of 160 ms. Over the ensuing 30 minutes, there was progressive narrowing of the QRS. A 12-lead ECG obtained on arrival in the emergency department (ED) 44 minutes later demonstrated a QRS duration of 94 ms. Initially, EMS ECG rhythm strips were unavailable and an isolated benzonatate ingestion was considered less likely as ECG intervals were normal. Benzonatate exposure was later confirmed with a urine benzonatate concentration, which was 8.5 mcg/mL. The patient made a full recovery.

DISCUSSION

Cases of pediatric benzonatate overdose with rapid development of cardiac arrest and full recovery have been previously reported. In this case, evidence of cardiac sodium channel blockade was demonstrated with a prolonged QRS interval on initial ECG rhythm strip analysis. However, unlike previous cases, rapid resolution of QRS prolongation occurred in this case. While transient QRS prolongation may be observed, finding a normal QRS interval should not discount the possibility of benzonatate overdose.

A description of the clinical course of severe benzonatate poisonings reported in the literature and to NPDS: A systematic review supplemented with NPDS cases

BACKGROUND

Benzonatate is a commonly prescribed medication that can be lethal in acute overdose of a small number of capsules.

OBJECTIVE

This was a systematic review to describe the course of severe poisoning and deaths from benzonatate supplemented with the National Poison Data System (NPDS) fatalities module.

METHODS

The NPDS was queried from 2000 to 2018 for benzonatate fatalities. Pubmed, Cochrane, Embase, and Google Scholar were searched for combinations of benzonatate and "poisoning," "overdose," and "toxicity." References of relevant articles were searched for additional publications. Articles were included if they described the clinical course of at least one patient suffering from benzonatate poisoning and available in English. Dual independent review and extraction were performed.

RESULTS

Seventeen cases from NPDS and 19 published reports met the inclusion criteria resulting in 36 cases, mostly (28/36) self-harm ingestions. Most patients were young [17 (11-29), median (IQR)] and female (22). Onset of toxicity was rapid at <5 min (9). Most common symptoms included cardiac arrest (29), seizures (24), and dysrhythmias (24). Treatments included intubation (26), cardiopulmonary resuscitation (28), vasopressors (20) and others. Return of spontaneous circulation was achieved in 23/28 patients, but most had significant neurologic deficits or other end organ damage and 5 survived with a good neurologic outcome.

CONCLUSION AND RELEVANCE

Overdose ingestions of benzonatate can cause significant toxicity with a rapid onset. Interventions performed were generally supportive in nature. Duration of directly toxic effects is short, but dramatic with neurologic devastation and resuscitated patients often still have a poor outcome.

Development and validation of LC-MS method for the determination of heptaethylene glycol monomethyl ether in benzonatate bulk drugs

A simple and isocratic reverse-phase liquid chromatography with mass spectrometric method has been developed and validated for the determination of heptaethylene glycol monomethyl ether in benzonatate drug substance. Benzonatate is an oral antitussive drug used to relieve and suppress cough in patients older than 10 years. The presence of residual heptaethylene glycol monomethyl ether in the benzonatate drug substance affects the safety, strength, purity and quality of the drug substance. The subject compound separation was achieved using 0.1% formic acid and acetonitrile (50:50 v/v) at a flow rate of 0.3 ml/min. The Suplex PKB-100 250 × 4.6 mm, 5 μm LC column was used for a better peak shape. Detection was carried out at an m/z value of 341. The linearity curve showed a correlation of coefficient of >0.999. The precision and intermediate precision (RSD) were <7.30. The accuracy values were >90% for all levels. The developed method was validated as per International Conference on Harmonization guidelines and found to be a novel, specific and sensitive analytical method for determination of components of interest.

Review of FDA Amendments Act Section 921 Experience in Posting Data-mining Results from the FAERS Database

PURPOSE

Title IX, § 921 of the Food and Drug Administration (FDA) Amendments Act of 2007 requires the FDA to mine data on a regular basis, using its adverse events database, the FDA Adverse Event Reporting System, to identify potential signals of serious risks/new safety information. This review of the FDA's quarterly web-posted results is the first to document the contributions of the program to maintaining the continued safe use of approved pharmaceutical drugs/biologics and the lessons that have emerged from this rich experience.

METHODS

Details on proprietary prescription drugs/biologics, generic prescription drugs, and over-the-counter drugs were downloaded from the quarterly posts that begin in first quarter of 2008. Key information was tabulated, including proprietary and generic names of products or classes of products, the identified potential signals of serious risks, the labeling-decision category (updated, no action is necessary at this time, or evaluating the need for regulatory action), the labeling section (Warnings and Precautions, Adverse Reactions, Drug Safety Communications, Contraindications, or Boxed Warnings), and estimated times to updated decisions.

FINDINGS

Since the beginning of the FDAAA Section 921 posting requirement, the FDA has posted 555 potential signals of serious risk or new safety information. Of these, there have been 262 posts (47%) that resulted in decisions requiring updated product labeling, 75 posts (14%) that resulted in decisions that no action was necessary, and 218 posts (39%) indicating that the FDA was evaluating the need for regulatory action. Of the 262 posts that required updating one or more sections of a product label, there was a preponderance of Warnings and Precautions, with 172 (66%); followed by Adverse Reactions, with 114 (44%); Drug Safety Communications, 44 (18%); Contraindications, 27 (10%); and Boxed Warnings, 19 (7%). The median times to update decisions were 12 months for Warnings & Precautions, Adverse Reactions, and Boxed Warnings, and 11 months for Contraindications.

IMPLICATIONS

Important themes from the present analysis include the following: (1) nearly 80% of posts resulted in updated product labeling; (2) 20% of decisions concerned classes of proprietary and generic drug/biologic products; (3) product-use errors, such as name confusion, continue to be important; (4) the safe use of pharmaceuticals in children is gaining attention but still has a long way to go; and (5) drug-drug interactions are of continuing concern. The FDA Amendments Act § 921 program will continue to have an important place in the future of pharmacovigilance practices.

Arrhythmogenic Antitussive: A Case of Pediatric Benzonatate Overdose With Torsades de Pointes, Cardiac Arrest, and Complete Recovery Without Neurologic Deficits

Benzonatate is a commonly prescribed antitussive with rapid and deadly effects in overdose. We report a 14-year-old female who ingested 14 capsules containing 200 mg benzonatate. Her case represents the only reported benzonatate overdose with torsades de pointes, as well as the only reported pediatric benzonatate ingestion complicated by cardiac arrest with full recovery.

Looking ahead to novel therapies for chronic cough. Part 1 - peripheral sensory nerve targeted treatments

INTRODUCTION

Due to a relatively high prevalence and negative impact on quality of life chronic cough (CC) is a challenge for both patients and clinicians. There is ongoing research to address the unmet need and develop more effective antitussive treatment options. This is the first part of a series of two reviews of new antitussive medications. Medical databases (Medline, Embase and SCOPUS) and trial registries (ClinicalTrials.gov and EudraCT) were searched for studies on antitussive drugs targeting peripheral sensory nerves.

AREAS COVERED

This review presents current knowledge of peripheral receptors that are not only involved in evoking the cough reflex, but are also potentially responsible for more sustained neural alterations. Blockage of the receptors and ion channels is discussed in terms of its potential antitussive effect.

EXPERT OPINION

Although better understanding of CC mechanisms has facilitated the development of novel treatments including P2X2/3 receptor inhibitors (e.g. gefapixant), there remain several gaps in the knowledge about the mechanisms and treatment of CC. These include the lack of tests to diagnose cough hypersensitivity syndrome and predictors of response to specific treatments. Further research into cough phenotypes and endotypes will yield important insights and a personalized approach to cough management.