Optimizing patient safety by preventing combined use of intramuscular olanzapine and parenteral benzodiazepines

Comparing the cardiorespiratory safety of parenteral olanzapine and benzodiazepines to parenteral haloperidol/droperidol and benzodiazepines in emergency department patients

INTRODUCTION

This study sought to assess the cardiorespiratory safety of parenteral olanzapine and benzodiazepine combination treatment compared to parenteral droperidol or haloperidol and benzodiazepine combination treatment.

MATERIALS AND METHODS

This was a retrospective chart review conducted in adult emergency department patients who received intramuscular (IM) or intravenous (IV) droperidol, haloperidol, or olanzapine within one hour of IM or IV benzodiazepine. Patients were stratified into groups based on whether they received either olanzapine in combination with a benzodiazepine (n = 48) or droperidol or haloperidol in combination with a benzodiazepine (n = 48).

RESULTS

Patients in each group had a decrease in their systolic blood pressure (SBP) after IM/IV olanzapine and IM/IV droperidol or haloperidol when used in combination with an IM/IV benzodiazepine ((Olanzapine + benzodiazepine (mmHg), median (IQR): Pre-SBP: 132 (117-151) vs. Post-SBP: 117 (99-131), p < 0.01) (Droperidol or haloperidol + benzodiazepine (mmHg), median (IQR): Pre-SBP: 138 (122-149) vs. Post-SBP: 106 (98-127), p < 0.01)). Both groups had similar percent SBP decreases post-combination treatment (Olanzapine + benzodiazepine (15.6 %) vs. Droperidol or haloperidol + benzodiazepine (15.2 %); p = 0.55). We did not observe any statistically significant between group differences for hypotension (Olanzapine + benzodiazepine: 1/48, 2.1 % vs. Droperidol or haloperidol + benzodiazepine: 3/48, 6.3 %; p = 0.62)), escalation in oxygen requirements (Olanzapine + benzodiazepine: 7/48, 14.6 %) vs. Droperidol or haloperidol + benzodiazepine: 5/48, 10.4 %; p = 0.76)), or intubation due to cardiorespiratory depression (Olanzapine + benzodiazepine: 0/0, 0 % vs. Droperidol or haloperidol + benzodiazepine: 0/0, 0 %; p = 1.00)).

CONCLUSION

This study found decreases in SBP after administering parenteral olanzapine and parenteral droperidol or haloperidol in combination with a parenteral benzodiazepine. The percent change in SBP and the frequency of hypotensive episodes post-combination treatment were not different between groups. There were also no differences between groups in need of increased oxygen requirements post-combination treatment or need for intubation due to cardiorespiratory depression. This study suggests parenteral olanzapine in combination with a parenteral benzodiazepine may have comparable cardiorespiratory safety versus parenteral droperidol or haloperidol in combination with a parenteral benzodiazepine when treating agitation in the adult ED.

Comparing Intubation Rates in Patients Receiving Parenteral Olanzapine With and Without a Parenteral Benzodiazepine in the Emergency Department

STUDY OBJECTIVE

United States prescribing information recommends against coadministration of injectable olanzapine with injectable benzodiazepines due to a risk of cardiorespiratory depression, whereas European prescribing information recommends the 2 drugs not be administered within 60 minutes of each other. In contrast, a recently published American College of Emergency Physicians clinical policy recommends injectable olanzapine and benzodiazepines be coadministered for treating severe agitation. We sought to compare injectable olanzapine with and without injectable benzodiazepines for evidence of cardiorespiratory depression.

METHODS

We performed a retrospective study of patients in an urban emergency department from January 2017 through November 2019 who received parenteral olanzapine with or without parenteral benzodiazepines. We included patients receiving 2 total medication doses, either olanzapine+benzodiazepine or 2 doses of olanzapine, coadministered within 60 minutes. The primary outcome was tracheal intubation in the emergency department. Secondary outcomes included hypotension (systolic blood pressure less than 90 mmHg) and hypoxemia (SpO2 less than 90%).

RESULTS

We identified 693 patients (median [alcohol]=210 mg/dL, median age=37 years [IQR 29 to 49]). In total, 549 received 2 doses of olanzapine, and 144 patients received olanzapine and a benzodiazepine. We found no difference in intubation rates between the olanzapine-only group (21/549, 3.8%) and the olanzapine+benzodiazepine group (5/144, 3.5%; difference=0.3%, 95% confidence interval -3.0% to 3.7%). Rates of hypoxemia (2% olanzapine-only and 3% olanzapine+benzodiazepine) and hypotension (9% both groups) also were not different between groups.

CONCLUSION

We found no difference in cardiorespiratory depression between patients receiving only olanzapine versus olanzapine plus a benzodiazepine.

Coadministration of intramuscular olanzapine and benzodiazepines in agitated patients with mental illness

Introduction:

Intramuscular antipsychotics are commonly used to manage agitated patients. In 2005, Eli Lilly placed a warning on olanzapine's prescribing information following post-marketing reports of fatal drug reactions when intramuscular olanzapine was used in the setting of benzodiazepines. Data is lacking examining this drug combination.

Methods:

A medication use evaluation was conducted at a county psychiatric hospital surveying the usage of concomitant intramuscular olanzapine and lorazepam from October 1, 2016, to July 20, 2017. A literature search was conducted to review available evidence.

Results:

Ninety-one instances of the drug combination were discovered, with no serious adverse events following administration. Of these 91 patients, 41 received both medications within 60 minutes of each other. No instances of hypotension, bradycardia, bradypnea, or oxygen desaturation occurred following administration. The literature review yielded 1 randomized, placebo-controlled clinical trial, 3 retrospective chart reviews, and several case studies.

Discussion:

Data detailing a causal relationship between olanzapine/benzodiazepine combinations and serious adverse effects is lacking. Available evidence does not consistently support a strong cause and effect relationship. The results of this medication use evaluation are not consistent with the Food and Drug Administration warning. Further controlled research is needed to help define the actual risk of using concomitant intramuscular olanzapine and benzodiazepines.

Clinically significant drug interactions with atypical antipsychotics

Atypical antipsychotics [also known as second-generation antipsychotics (SGAs)] have become a mainstay therapeutic treatment intervention for patients with schizophrenia, bipolar disorders and other psychotic conditions. These agents are commonly used with other medications--most notably, antidepressants and antiepileptic drugs. Drug interactions can take place by various pharmacokinetic, pharmacodynamic and pharmaceutical mechanisms. The pharmacokinetic profile of each SGA, especially with phase I and phase II metabolism, can allow for potentially significant drug interactions. Pharmacodynamic interactions arise when agents have comparable receptor site activity, which can lead to additive or competitive effects without alterations in measured plasma drug concentrations. Additionally, the role of drug transporters in drug interactions continues to evolve and may effect both pharmacokinetic and pharmacodynamic interactions. Pharmaceutical interactions occur when physical incompatibilities take place between agents prior to drug absorption. Approximate therapeutic plasma concentration ranges have been suggested for a number of SGAs. Drug interactions that markedly increase or decrease the concentrations of these agents beyond their ranges can lead to adverse events or diminished clinical efficacy. Most clinically significant drug interactions with SGAs occur via the cytochrome P450 (CYP) system. Many but not all drug interactions with SGAs are identified during drug discovery and pre-clinical development by employing a series of standardized in vitro and in vivo studies with known CYP inducers and inhibitors. Later therapeutic drug monitoring programmes, clinical studies and case reports offer methods to identify additional clinically significant drug interactions. Some commonly co-administered drugs with a significant potential for drug-drug interactions with selected SGAs include some SSRIs. Antiepileptic mood stabilizers such as carbamazepine and valproate, as well as other antiepileptic drugs such as phenobarbital and phenytoin, may decrease plasma SGA concentrations. Some anti-infective agents such as protease inhibitors and fluoroquinolones are of concern as well. Two additional important factors that influence drug interactions with SGAs are dose and time dependence. Smoking is very common among psychiatric patients and can induce CYP1A2 enzymes, thereby lowering expected plasma levels of certain SGAs. It is recommended that ziprasidone and lurasidone are taken with food to promote drug absorption, otherwise their bioavailability can be reduced. Clinicians must be aware of the variety of factors that can increase the likelihood of clinically significant drug interactions with SGAs, and must carefully monitor patients to maximize treatment efficacy while minimizing adverse events.