- Author: Chip Gresham, MD, FACEM; Chief Editor: Asim Tarabar, MD more...
Oral benzodiazepine (BZD) overdoses, without co-ingestions, rarely result in significant morbidity (eg, aspiration pneumonia, rhabdomyolysis) or mortality. In mixed overdoses, they can potentiate the effect of alcohol or other sedative-hypnotics. Acute intravenous administration of BZDs is associated with greater degrees of respiratory depression.
Patients receiving prolonged parenteral administration of BZDs are at risk for propylene glycol poisoning (the diluent used in parenteral formulations of diazepam and lorazepam). Although rare, this may result in hypotension, cardiac dysrhythmias, lactic acidosis, seizures, or coma.
Signs and symptoms
Symptoms of BZD overdose may include the following:
Findings on physical examination may include the following:
Altered mental status, impairment of cognition
See Clinical Presentation for more detail.
Immunoassay screening techniques are performed most commonly. These tests typically detect BZDs that are metabolized to desmethyldiazepam or oxazepam; thus, a negative screening result does not rule out the presence of a BZD.
Tests and procedures depend on the presentation, as follows:
Obtain an arterial blood gas (ABG) if respiratory depression is present
Obtain an ECG to evaluate for co-ingestants, particularly cyclic antidepressants
Obtain a chest radiograph if respiratory compromise is present
Obtain a pregnancy test in women of childbearing age
In patients with an intentional overdose, measure the following:
See Workup for more detail.
As with any overdose, the first step is an assessment of the patient's airway, breathing, and circulation, and these should be addressed rapidly as needed. In any patient with an altered mental status, a blood glucose level should be obtained immediately. The cornerstone of treatment in BZD overdoses is good supportive care and monitoring. Single-dose activated charcoal is not routinely recommended as the risks far outweigh the benefit. BZDs are very rarely fatal in overdoses, although the resulting altered mental status greatly increases the risk of aspiration following oral charcoal dose.
Flumazenil (Romazicon) is a specific antidote for BZD poisoning, although its use in acute BZD overdose is controversial and its risks usually outweigh any possible benefit. In long-term BZD users, flumazenil may precipitate withdrawal and seizures; in patients taking BZDs for a medical condition, flumenazil may result in exacerbation of the condition. The ideal indication for flumazenil is isolated iatrogenic BZD overdose in BZD-naive patients (eg, during conscious sedation on BZD-naive patient).
Benzodiazepine (BZD) toxicity may result from overdose or from abuse. Since their introduction in 1960, BZDs have come to be widely used for a variety of indications, including seizures, anxiety, alcohol withdrawal, insomnia, drug-associated agitation, and muscle spasm. In addition, BZDs are used as preanesthetic agents, and are frequently combined with other medications for procedural sedation. BZD overdose often occurs in association with other substances.
For patient education resources, see the Poisoning - First Aid and Emergency Center, Mental Health and Behavior Center, and Substance Abuse Center, as well as Benzodiazepine Abuse, Drug Overdose, Activated Charcoal, and Poison Proofing Your Home.
Benzodiazepines (BZDs) act by potentiating the activity of gamma-aminobutyric acid (GABA), which is the major inhibitory neurotransmitter in the central nervous system (CNS). BZDs bind to a specific receptor on the GABA A receptor complex and thereby facilitate the binding of GABA to its specific receptor site. BZD binding causes increased frequency of opening of the chloride channel complexed with the GABA A receptor. Chloride channel opening results in membrane hyperpolarization, which inhibits cellular excitation.
Enhanced GABA neurotransmission results in sedation, striated muscle relaxation, anxiolysis, and anticonvulsant effects. Stimulation of peripheral nervous system (PNS) GABA receptors may cause decreased cardiac contractility and vasodilation. These changes could have the potential to alter tissue perfusion.
The rate of BZD onset of action is determined by its ability to cross the blood-brain barrier. The relatively lipophilic BZDs (eg, diazepam) usually have a faster onset of effect than the relatively water-soluble BZDs (eg, lorazepam). BZD effects can be potentiated when ethanol is present as a coingestant. Peak blood concentrations of most agents occur within 1-3 hours.
After a single dose, the lipophilic agents can have a shorter duration of action (shorter CNS effect) than water-soluble agents because rapid redistribution from the CNS to peripheral sites (eg, adipose tissue); thus, lorazepam has a longer CNS duration of action than diazepam. However, diazepam metabolizes to active intermediates with prolonged half-lives, which extend its therapeutic effects.
BZDs are metabolized predominantly in the liver by oxidation and/or conjugation. Most BZDs are broken down into pharmacologically active metabolites, which may have longer half-lives than the parent compounds.
According to the Drug Abuse Warning Network (DAWN) of the US Department of Health and Human Services, total emergency department (ED) visits for nonmedical use of BZDs rose 149% from 2004 to 2011. However, no short-term increases were noted between 2009 and 2011. Records did not always specify the BZD involved, but alprazolam was indicated in about a third of these ED visits, and in approximately a third of BZD-related suicide attempts
DAWN was discontinued in 2011. ED data from the new data collection system are expected in 2017.
In 2014, a total of 27,060 benzodiazepine (BZD) single-substance exposures were reported to US poison control centers. Of these, 370 (1.4%) resulted in major toxicity and 18 (0.07%) resulted in death. Inclusion of cases involving BZDs in combination with alcohol or other drugs yields much higher numbers. DAWN has reported that BZDs were involved in 123,572 of the 606,653 ED visits in 2011 that involved drugs and alcohol taken together (20.4%).
Although BZDs taken alone are relatively safe in overdose, the combination of BZDs and opioid analgesics can produce significant respiratory depression. In particular, the combination of alprazolam with opioids may be fatal. Analysis of a West Virginia forensic database showed that alprazolam contributed to 17% of drug-related deaths; at least one other drug, typically an opioid, was identified in 97.5% of the alprazolam cases, with concurrent BZDs also found.
Deaths attributed to BZDs increased fivefold from 1999 to 2009. During 2003 to 2009, death rates from alprazolam increased 233.8%; alprazolam was second only to oxycodone among prescription drugs with the highest increase in death rates.
Similarly, an Australian study reported that alprazolam-positive cases of sudden or unnatural death increased from three cases in 1997 to 86 cases in 2012. The increase was driven mostly by accidental toxicity in people with known drug and alcohol problems. Drugs other than alprazolam and its metabolites were present in 94.9% of cases. The most commonly detected drugs, in order of decreasing frequency, were opioids, other benzodiazepines, and alcohol.
The most reported BZD use is in persons older than 19 years. Elderly individuals and very young persons are more susceptible to the CNS depressant effects of BZDs than people in other age groups.
Oral benzodiazepine (BZD) overdoses, without co-ingestions, rarely result in significant morbidity (eg, aspiration pneumonia, rhabdomyolysis) or mortality, although in mixed overdoses they can potentiate the effect of alcohol or other sedative-hypnotics. Overdose of ultrashort-acting BZDs (eg, triazolam [Halcion]) is also more likely to result in apnea and death than overdose with longer-acting BZDs. Of individual BZDs, aprazolam is relatively more toxic than others in overdose.
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