Based on 10,225 NEISS-CADES cases, US adults aged ≥ 20 years made an estimated 145,490 (95% CI, 115,279–175,701) ED visits for AEs from antibiotics each year in 2011–2015, causing 13.7% (95% CI, 12.3–15.2%) of estimated adult ED visits for AEs from all systemically administered medications (Table 1). One third (33.0%) of estimated ED visits for antibiotic AEs involved adults 20 to 34 years of age, representing 27.1% (95% CI, 25.1–29.1%) of estimated ED visits for AEs from all systemically administered medications in young adults. Adults younger than 50 years of age were involved in over one half (56.6%) of estimated ED visits for AEs from antibiotics (95% CI, 54.8–58.4%), but less than a third (31.0%) of estimated ED visits for AEs from all other systemically administered medications (95% CI, 27.7–34.3%).
Table 1 US Emergency Department (ED) Visits Among Adults for Adverse Events (AEs) from Systemically Administered Medications, by Case Characteristics, 2011–2015 The population rate of estimated ED visits for AEs from antibiotics was similar for younger and older age groups (7.3 per 10,000 individuals aged 20–34 years [95% CI, 5.8–8.9] versus 6.7 per 10,000 individuals aged ≥ 65 years [95% CI, 5.1–8.3]). In contrast, the population rate of estimated ED visits for AEs from non-antibiotic, systemically administered medications increased significantly with age, from 19.7 per 10,000 individuals aged 20–34 years (95% CI, 16.0–23.4) to 90.0 per 10,000 individuals aged ≥ 65 years (95% CI, 61.2–118.9).
Accounting for prescribing frequency of oral antibiotics, young adults aged 20–34 years had twice the estimated rate of ED visits for AEs from oral antibiotics compared with those aged ≥ 65 years (9.7 visits per 10,000 dispensed prescriptions versus 4.6 visits per 10,000 dispensed prescriptions; 95% CI, 7.6–11.8 versus 3.6–5.7). The estimated rate of ED visits for AEs from oral antibiotics among females was 7.2 per 10,000 dispensed prescriptions (95% CI, 5.8–8.7), compared with 5.0 per 10,000 dispensed prescriptions among males (95% CI, 3.9–6.0) (Online Supplementary Table).
Females accounted for 71.8% of estimated ED visits for AEs from antibiotics, compared with 56.3% of visits due to AEs from non-antibiotics (Table 1). A single medication was almost always implicated in ED visits for antibiotic AEs (86.4%), and nearly all estimated ED visits for antibiotic AEs were attributed to oral preparations (96.9%; 95% CI, 96.2–97.6%). Allergic reactions were more common among ED visits for antibiotic AEs, compared with AEs from non-antibiotics (74.3 versus 15.9%), and ED visits for antibiotic AEs less commonly had documented medication errors (2.4 versus 12.5%) or required hospitalization (9.2 versus 32.4%).
Antibiotic Classes Implicated in Adverse Events
The three most frequently implicated antibiotic classes in ED visits by adults for AEs were oral sulfonamides (23.2%), penicillins (20.8%), and quinolones (15.7%) (Table 2). Oral oxazolidinones (linezolid) accounted for just 0.2% of ED visits for antibiotic AEs but, accounting for dispensed prescriptions from retail and long-term care pharmacies, had the highest estimated rate of ED visits for AEs (19.9 ED visits per 10,000 dispensed prescriptions), followed by oral sulfonamides (19.4 ED visits per 10,000 dispensed prescriptions) and lincomycins (clindamycin) (13.2 ED visits per 10,000 dispensed prescriptions).
Table 2 US Emergency Department (ED) Visits Among Adults for Adverse Events (AEs) from Antibiotics, by Drug Class, 2011–2015 Antibiotic Drug Products Implicated in Adverse Events
Sulfamethoxazole/trimethoprim was the most commonly implicated oral antibiotic product across all age groups, accounting for between one fifth (19.7%) and one quarter (25.8%) of estimated ED visits for oral antibiotic AEs (Table 3). Amoxicillin was the second most commonly implicated oral antibiotic product among adults aged 20–34, 35–49, and 50–64 years, accounting for an estimated 14.6, 10.8, and 11.0% of visits, respectively, while among older adults aged ≥ 65 years, ciprofloxacin was the second most commonly implicated oral antibiotic product (12.2%).
Table 3 US Emergency Department (ED) Visits Among Adults for Adverse Events (AEs) from Oral Antibiotics, by Patient Age and Drug Product, 2011–2015 Prescription-based estimated rates of ED visits for AEs from oral antibiotics generally decreased with increasing patient age group. For example, the estimated rate for oral sulfamethoxazole/trimethoprim was 29.7 (95% CI, 21.9–37.5) ED visits per 10,000 dispensed prescriptions among young adults aged 20–34 years, compared with 11.4 (95% CI, 8.4–14.4) per 10,000 dispensed prescriptions among older adults aged ≥ 65 years.
Moxifloxacin had the highest estimated rate of ED visits for AEs from oral antibiotics across all ages, at 30.1 ED visits per 10,000 dispensed prescriptions (95% CI, 20.2–40.0), a rate five to six times that of the oral fluoroquinolones ciprofloxacin and levofloxacin (5.8 and 5.7 ED visits per 10,000 dispensed prescriptions, respectively; 95% CI, 4.2–7.4 and 4.5–6.9). After moxifloxacin, oral antibiotics with the highest estimated rates were linezolid (19.9 ED visits per 10,000 dispensed prescriptions; 95% CI, 8.2–31.5), sulfamethoxazole/trimethoprim (19.1 ED visits per 10,000 dispensed prescriptions; 95% CI, 14.7–23.5), and clindamycin (13.2 ED visits per 10,000 dispensed prescriptions; 95% CI, 10.4–16.0).
Adverse Event Manifestations
Mild allergic reactions (e.g., rash, pruritus) were the most commonly documented adverse event manifestation across all oral antibiotic classes (Table 4), and accounted for over two thirds of estimated visits involving sulfonamides (69.3%). Moderate-to-severe allergic reactions (e.g., anaphylaxis, angioedema) occurred in approximately one quarter of estimated ED visits for AEs involving oral quinolones (26.2%), and allergic reactions of any severity accounted for 87.2% (95% CI, 84.7–89.7%) of estimated ED visits for AEs involving oral sulfonamides. Gastrointestinal disturbance (e.g., nausea, diarrhea, abdominal pain) was documented in approximately one quarter of estimated visits involving oral nitroimidazoles (metronidazole) (28.3%), macrolides (27.0%), and tetracyclines (25.4%).
Table 4 US Emergency Department (ED) Visits Among Adults for Adverse Events (AEs) from Oral Antibiotics, by Drug Class and AE Manifestation, 2011–2015 Oral sulfonamides had the highest estimated rates of ED visits for mild allergic reactions (13.4 visits per 10,000 dispensed prescriptions; 95% CI, 10.0–16.8) and moderate-to-severe allergic reactions (3.5 visits per 10,000 dispensed prescriptions; 95% CI, 2.6–4.3). While the overall rate of ED visits for moderate-to-severe allergic reactions to oral quinolones (1.7 visits per 10,000 dispensed prescriptions; 95% CI, 1.3–2.1) was lower than that for sulfonamides, moxifloxacin had significantly higher estimated rates of ED visits for moderate-to-severe allergic reactions (9.7 visits per 10,000 dispensed prescriptions; 95% CI, 5.9–13.4) compared with sulfonamides. The estimated rate of ED visits for moderate-to-severe allergic reactions to moxifloxacin was significantly higher than rates for the other oral quinolones levofloxacin (1.7 per 10,000 dispensed prescriptions; 95% CI, 1.3–2.2) and ciprofloxacin (1.3 per 10,000 dispensed prescriptions; 95% CI, 1.0–1.6).