The Pharmacology of Respiratory Depressants and Stimulants

The Use of Benzodiazepine Receptor Agonists and Risk of Respiratory Failure in Patients with Chronic Obstructive Pulmonary Disease: A Nationwide Population-Based Case-Control Study

STUDY OBJECTIVES

Insomnia is prevalent in patients with chronic obstructive pulmonary disease (COPD), and benzodiazepine receptor agonists (BZRAs) are the most commonly used drugs despite their adverse effects on respiratory function. The aim of this study was to investigate whether the use of BZRAs was associated with an increased risk of respiratory failure (RF) in COPD patients.

DESIGN

Matched case-control study.

SETTING

National Health Insurance Research Database (NHIRD) in Taiwan.

PARTICIPANTS

The case group consisted of 2,434 COPD patients with RF, and the control group consisted of 2,434 COPD patients without RF, matched for age, sex, and date of enrollment.

MEASUREMENTS AND RESULTS

Exposure to BZRAs during the 180-day period preceding the index date was analyzed and compared in the case and control groups. Conditional logistic regression was performed, and the use of BZRAs was associated with an increased risk of RF (adjusted odds ratio [aOR] 1.56, 95% confidence interval [CI] 1.14-2.13). In subgroup analysis, we found that the benzodiazepine (BZD) users had a higher risk of RF (aOR 1.58, 95% CI 1.14-2.20), whereas the risk in non-benzodiazepine (non-BZD) users was insignificant (aOR 0.85, 95% CI 0.51-1.44). A greater than 2-fold increase in risk was found in those who received two or more kinds of BZRAs and those using a combination of BZD and non-BZD medications.

CONCLUSIONS

The use of benzodiazepine receptor agonists was a significant risk factor for respiratory failure in patients with chronic obstructive pulmonary disease (COPD). Compared to benzodiazepine, the prescription of non-benzodiazepine may be safer for the management of insomnia in COPD patients.

Toxicokinetics/Toxicodynamics of γ-hydroxybutyrate-ethanol intoxication: evaluation of potential treatment strategies

γ-Hydroxybutyrate (GHB), a common drug of abuse, is often coingested with ethanol. Increasing renal clearance via monocarboxylate transporter (MCT) inhibition represents a potential therapeutic strategy in GHB overdose, as does inhibition of GABAB receptors. In this study, we investigate toxicokinetic/toxicodynamic interactions between GHB-ethanol and efficacy of treatment options for GHB-ethanol intoxication in rats. Sedation was assessed using the endpoint of return-to-righting reflex. Respiration was assessed using plethysmography. Coadministration of 2.0 g/kg ethanol i.v. with 600 mg/kg GHB i.v. increased sleep time compared with GHB alone. Administration of ethanol to steady-state concentrations of 0.1-0.2% and 0.3-0.4% (w/v) did not affect toxicokinetics of 600 mg/kg GHB i.v., or respiratory rate, but did result in significantly lower peak tidal volumes compared with GHB alone. Oral administration of 2.5 g/kg ethanol had no significant effect on toxicokinetics of 1500 mg/kg orally administered GHB. Pretreatment with specific receptor inhibitors indicated no effect of GABAA receptor inhibition on sleep time or respiratory depression in GHB-ethanol intoxication. GABAB receptor inhibition partially prevented sedation and completely prevented respiratory depression. Ethanol increased fatality when administered at 0.1-0.2% (4 of 10) and 0.3-0.4% (9 of 10) versus 1500 mg/kg GHB i.v. alone (0 of 10). Treatment with the MCT inhibitor, l-lactate, significantly decreased sleep time after GHB-ethanol and decreased fatality at 0.1-0.2% (0 of 10) and 0.3-0.4% ethanol (5 of 10). Treatment with a GABAB receptor antagonist completely prevented fatality at 0.3-0.4% (0 of 10). These data indicate that ethanol potentiates the sedative and respiratory depressant effects of GHB, increasing the risk of fatality. MCT and GABAB receptor inhibition represent potentially effective treatments in GHB-ethanol intoxication.

Management of insomnia in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common medical disorder, which causes considerable morbidity and mortality. Given the chronic and symptomatic nature of the disease, the patient is often seen in the physician's office with complaints of dyspnea. However, more than 50% of COPD patients also have sleep complaints characterised by longer latency to falling asleep, more frequent arousals and awakenings, and/or generalised insomnia. Sleep disturbance tends to be more severe with advancing disease and substantially reduces the COPD patients' quality of life. In approaching the COPD patient who complains of insomnia it is important to take a complete sleep history. Having characterised the degree and duration of the problem, medical management of the underlying COPD must first optimise oxygen saturation while minimising the effects of many of the medications used for COPD. While aerosol therapies may be systemically absorbed and contribute to sleep disruption, anticholinergics, such as ipratropium bromide, are the least likely to do so and indeed have been shown to improve sleep quality in this population. Many of the traditional sedatives and hypnotics have been used in the COPD population including benzodiazepines, imidazopyridines, pyrazolopyrimidines and, less commonly, antidepressants and phenothiazines. Clinical trials support the role of numerous agents in treating insomnia in this population but do not always provide reassurance that these therapies can be used safely, particularly in the patient with severe COPD with hypercarbia. Benzodiazepines are among the most commonly employed agents, but case reports and series continue to describe adverse pulmonary events. Although the newer pyridine derivatives also have the potential to worsen pulmonary function, they appear less likely to do so. Data to date are limited with the tricyclic antidepressants and phenothiazines, although they appear to be very well tolerated from a respiratory point of view. Since sleep disturbances are often long-standing and associated with maladaptive behaviours towards sleep, cognitive/behavioural approaches are often useful and are more effective in the long-term than are hypnotics. When prescription of a sedative is to be made, extra caution is required for those patients at increased risk of adverse respiratory effects, such as those with advanced disease and hypercarbia in whom pharmacological therapy is often best avoided. Selection of the various options will depend upon the degree of underlying disease and the patient's specific complaints of insomnia. Finally, it is important to remember that while most hypnotics work in an acute setting, the long-term management will require an integrated approach.