Medicine by the Numbers

A Collaboration of and AFP

Combined Inhaled Short-Acting Beta2 Agonist and Anticholinergic Agents for Asthma


Am Fam Physician. 2018 Jun 1;97(11):online.


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1 in 16 avoided hospitalization

1 in 36 had adverse events (tremors, agitation, or palpitations)

1 in 20 avoided relapse



1 in 16 avoided hospitalization

1 in 36 had adverse events (tremors, agitation, or palpitations)

1 in 20 avoided relapse

Details for This Review

Study Population: Patients 16 years or older with asthma who presented to the emergency department (ED) with an asthma exacerbation

Efficacy End Points: Reduction in hospitalization, reduction in return visits to the ED

Harm End Points: Increase in adverse events such as tremors, agitation, and palpitations

Narrative: In the United States, 9% of patients who present with an asthma exacerbation require hospitalization.1 The direct costs for asthma treatment in the United States, including prescriptions, hospitalizations, and clinic and ED visits, total approximately $5.1 billion annually.2 For years, the mainstay of treatment for acute asthma exacerbations has been short-acting beta2 agonists (SABAs), such as albuterol. Albuterol works primarily to promote bronchodilation. Additionally, short-acting anticholinergics, such as ipratropium (Atrovent), work to reduce bronchorrhea and have a milder impact on bronchodilation than SABAs. The combination of SABAs and short-acting anticholinergics has been studied and suggests a possible synergistic effect that lengthens symptom management and reduces the need for inpatient stays.

This Cochrane review included 23 controlled or randomized trials with a total of 2,724 patients.3 Sixteen of these trials (2,120 participants) found that those receiving combined short-acting anticholinergic and SABA therapy had a lower rate of hospitalization than those receiving a SABA alone (relative risk [RR] = 0.72; 95% confidence interval [CI], 0.59 to 0.87). The estimated 65 fewer patients per 1,000 admitted to the hospital (166 vs. 231, respectively) translates to a number needed to treat (NNT) of 16. Five studies of 1,180 patients examined relapse, defined as a return to the ED with worsening symptoms within 24 hours.

Author disclosure: No relevant financial affiliations.

Copyright 2018 The NNT Group ( Used with permission.

This series is coordinated by Dean A. Seehusen, MD, MPH, AFP Assistant Medical Editor, and Daniel Runde, MD, from the NNT Group.

A collection of Medicine by the Numbers published in AFP is available at


1. Adams RJ, Fuhlbrigge A, Guilbert T, Lozano P, Martinez F. Inadequate use of asthma medication in the United States: results of the asthma in America national population survey. J Allergy Clin Immunol. 2002; 110(1):58–64.

2. Smith DH, Malone DC, Lawson KA, Okamoto LJ, Battista C, Saunders WB. A national estimate of the economic costs of asthma. Am J Respir Crit Care Med. 1997;156(3 pt 1):787–793.

3. Kirkland SW, Vandenberghe C, Voaklander B, Nikel T, Campbell S, Rowe BH. Combined inhaled beta-agonist and anticholinergic agents for emergency management in adults with asthma. Cochrane Database Syst Rev. 2017;(1):CD001284.



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