February 28, 2011

Antibiotic Prescribing and Use

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CHRT Issue Brief February 2011

The Institute of Medicine and the Centers for Disease Control and Prevention (CDC) have identified antibiotic resistance as a major public health problem in our country.1 One of the biggest contributors to antibiotic resistance is the inappropriate use of antibiotics.

Of particular concern is the prescribing of antibiotics for infections that are usually viral in nature—colds, sore throats, and most upper respiratory infections. These illnesses do not respond to antibiotics and nearly always get better on their own. Since 1995 the CDC has run an outreach campaign to encourage appropriate use of antibiotics, and the overall rate of antibiotic prescribing decreased 23 percent from 1992 to 2000. Nevertheless, a high rate of inappropriate antibiotic use—a rate that continues to put population health at risk—persists. This issue brief examines antibiotic prescribing trends in Michigan in recent years.

1 Mark S. Smolinski, Margaret A. Hamburg, and Joshua Lederberg, Editors, Committee on Emerging Microbial Threats to Health in the 21st Century. (2003). Microbial Threats to Health: Emergence, Detection, and Response. Washington, D.C.: The National Academies Press.

Trends in Antibiotic Use

Two million antibiotic prescriptions were billed to Blue Cross Blue Shield of Michigan (BCBSM) in 2009; more were likely dispensed that cost less than the co-payment. The BCBSM data show that members are prescribed just under one (.9) antibiotic per year. This is comparable to the national average of .88 prescriptions per person.2

Overall antibiotic prescribing for adult BCBSM members decreased 9.3 percent between 2007 and 2009, from .96 prescriptions per member to .87 prescriptions per member.

Figure IB6:1
Antibiotic Prescribing Rate, Adults, BCBSM, 2007–2009

figure-1
  200720082009
Prescriptions per 1000 Members 959 922 870

Many of the CDC-initiated outreach activities aimed at reducing inappropriate antibiotic use have been focused on pediatricians.3 Despite these efforts, antibiotic prescribing rates for BCBSM children increased 4.5 percent between 2007 and 2009. The overall increase in antibiotic use combined with data presented later in this issue brief indicates that there continues to be too high a rate of inappropriate use.

Figure IB6:2
Antibiotic Prescribing Rate, Children, BCBSM, 2007–2009

figure-2
  200720082009
Prescriptions per 1000 Members 930 905 972

2 Steinman, M.A., Yang, K.Y., Byron, S.C., Maselli, J.H., & Gonzales, R. (2009). Variation in outpatient antibiotic prescribing in the United States. The American Journal of Managed Care, 15(12), 861–868.

3 Grijalva, C.G., Nuorti, J.P., & Griffin, M.R. (2009). Antibiotic prescription rates for acute respiratory tract infections in US ambulatory settings. JAMA: The Journal of the American Medical Association, 302(7), 758–766. doi:10.1001/jama.2009.1163

Types of Antibiotics Prescribed

The National Committee for Quality Assurance (NCQA) has identified a list of “antibiotics of concern.” These antibiotics are called “broad spectrum” antibiotics, meaning they are effective against a wide range of bacteria. While these drugs can be very valuable in treating infections that have not responded to other agents or were caused by multiple types of bacteria, in many cases an infection can be more precisely targeted with a narrow spectrum antibiotic. Since the use of any antibiotic agent can promote resistance to that agent, broad spectrum antibiotics should be reserved for the most serious infections. Overuse of these agents is of concern because it can cause increased resistance to them, leaving even fewer drugs available to treat serious infections.4

In 2009, 49.1 percent of antibiotic prescriptions in the overall BCBSM population were for these broad spectrum antibiotics. This compares to a national rate of 47 percent.2,5 Between 2007 and 2009, the percent of antibiotic prescriptions for antibiotics of concern stayed nearly steady in the adult BCBSM population, decreasing 0.4 percent during that time period. In the same time period, the percentage of antibiotics of concern prescribed to BCBSM children increased 3.4 percent, going from 44.9 percent to 46.4 percent. One possible explanation for this increase in children is the continuing rise in resistant pathogens that are responsible for ear infections in children, necessitating broad spectrum antibiotic treatment.6 Other possible reasons are that children get different infections than adults, and that some drugs that are used in adults are not used for pediatric patients.

Figure IB6:3
Percent of Antibiotic Prescriptions for Antibiotics of Concern, 2007–2009

figure-3
  200720082009
Adults 50.3% 51.2% 50.1%
Children 44.9% 45.3% 46.4%

4 Tenover, F.C., & Hughes, J.M. (1996). The Challenges of Emerging Infectious Diseases. JAMA: The Journal of the American Medical Association, 275(4), 300&nsahs;304. doi:10.1001/jama.1996.03530280052036

5 National rates are from a study of 229 managed care plans. BCBSM data is from PPO plans.

6 Naseri, I., Jerris, R.C., & Sobol, S.E. (2009). Nationwide Trends in Pediatric Staphylococcus aureus Head and Neck Infections. Arch Otolaryngol Head Neck Surg, 135(1), 14&nsash;16. doi:10.1001/ archoto.2008.511

When antibiotic prescribing is indicated, determining which antibiotic to prescribe is influenced by several factors. The most important factor should be which antibiotic is most effective against the bacteria likely to be responsible for a given infection. However, factors such as physician and patient preference, convenience, and familiarity with specific drugs often play a role.

Figure 4 shows the top antibiotics prescribed for BCBSM adults in 2009, highlighting those categorized by the NCQA as “antibiotics of concern.” Five of the top ten most common antibiotics are classified as “antibiotics of concern.” Azithromycin (also known as Zithromax or Z-Pak) is the most frequently prescribed antibiotic for adults, making up 20 percent of all antibiotic prescriptions.

Figure IB6:4
Top Antibiotic Drugs, Adults, BCBSM, 2009

Product NameBCBSM Total Spending in 2009Number of PrescriptionsPrice per Course
Azithromycin (Zithromax) $4,234,950.16 292,797 $14.46
Amoxicillin (Amoxil) $920,529.32 184,921 $4.98
Cephalexin Monohydrate (Keflex) $577,347.89 113,861 $5.07
Ciprofloxacin Hydrochloride (Cipro) $392,565.25 107,295 $3.66
Amoxicillin-Clavulanate (Augmentin) $2,131,969.68 88,257 $24.16
Sulfamethoxazole-Trimethoprim DS (Bactrim DS) $384,944.21 87,423 $4.40
Doxycycline Hyclate (Vibramycin) $532,470.62 75,536 $7.05
Levofloxacin (Levaquin) $6,566,226.78 59,525 $110.31
Clindamycin Hydrochloride (Cleocin) $498,133.18 53,473 $9.32
Penicillin V Potassium (Pen-V) $246,756.42 42,614 $5.79

The most commonly prescribed antibiotic for children in 2009 was Amoxicillin. Only three of the top ten antibiotics are categorized as “antibiotics of concern.”

Figure IB6:5
Top Antibiotic Drugs, Children, BCBSM, 2009

Product NameBCBSM Total Spending in 2009Number of PrescriptionsPrice per Course
Amoxicillin (Amoxil) $926,714.58 161,776 $5.73
Azithromycin (Zithromax, Z-Pak) $2,484,634.61 129,401 $19.20
Amoxicillin-Clavulanate (Augmentin) $1,312,709.55 51,664 $25.41
Cefdinir (Omnicef) $2,307,757.13 41,695 $55.35
Cephalexin Monohydrate (Keflex) $262,568.84 35,070 $7.49
Sulfamethoxazole-Trimethoprim (Bactrim) $156,157.36 17,221 $9.07
Minocycline Hydrochloride (Minocin) $303,914.09 15,159 $20.05
Sulfamethoxazole-Trimethoprim DS (Bactrim DS) $43,602.15 9,753 $4.47
Doxycycline Hyclate (Vibramycin) $49,590.39 9,401 $5.28
Penicillin V Potassium (Pen-V) $33,660.58 7,467 $4.51

Geographic Variation in Antibiotic Prescribing7

In general, we know antibiotic prescribing varies widely across regions, health plans, and even individual physicians.2 In Michigan, antibiotic prescribing rates among the BCBSM population vary across hospital service areas (HSA). These differences cannot be explained by different rates of illness alone.8

In the adult population in 2009, the highest overall antibiotic prescribing rate in Michigan was 2.2 times the lowest antibiotic prescription rate. Eleven HSAs had prescribing rates that were at least 30 percent higher than the state average: Cheboygan, Gaylord, Grosse Point, Hillsdale, L’anse, Ludington, Marlette, Pigeon, Sturgis, Watervliet, and West Branch. Five HSAs had prescribing rates 25 percent or less than the state average: Ann Arbor, Chelsea, Greenville, Saline, and Southfield.

Figure IB6:6
Antibiotic Prescribing for Adults, BCBSM, 2009

figure-6

Prescribing for the pediatric population showed much higher variation than prescribing for the adult population. In 2009, the rate of antibiotic prescribing for BCBSM children varied by a factor of 4.6, from .54 antibiotics per member in Ann Arbor to 2.2 antibiotics per member in Dowagiac. Thirty-six HSAs had rates more than 30 percent above the state average, while nine had rates at least 25 percent below the state average. Eight of the nine low utilizing HSAs were in Southeast Michigan. High utilizing HSAs were clustered in the Upper Peninsula, in Northern Lower Michigan, and on the Ohio border.

Southeast Michigan has a lower rate of antibiotic use in children and more pediatricians per 1000 population than outstate Michigan. Though there is not a statistically significant association between lower antibiotic use rates and higher numbers of pediatricians per 1000 population at the HSA level, it may account, at least in part, for differences that can be seen between southeast Michigan and the rest of the state.

Figure IB6:7
Antibiotic Prescribing for Children, BCBSM, 2009

figure-7

Figure IB6:8
Antibiotic Prescribing Rates and Appropriate Use Measures, BCBSM, 2009

HSATotal antibiotics prescribed per 1000 peopleAntibiotics prescribed per 1000 childrenPercent of children with upper respiratory infections given antibioticsPercent of children with pharangytis given appropriate testingAntibiotics prescribed per 1000 adultsPercent of adults with bronchitis prescribed antibiotics
Dowagiac 1370 2205 48.9% 44.2% 1070 n/a
Pigeon 1337 1936 42.3% n/a 1176 n/a
Hillsdale 1331 1607 19.3% 50.0% 1231 86.0%
Gaylord 1331 1897 40.0% 55.8% 1165 84.9%
Sturgis 1298 1689 49.2% 38.7% 1168 n/a
Cheboygan 1265 1569 19.8% 60.8% 1178 85.7%
Marlette 1253 1324 33.3% n/a 1230 n/a
Watervliet 1252 1576 32.1% 54.7% 1140 74.2%
Bad Axe 1249 1815 47.0% 11.0% 1044 87.9%
WestBranch 1223 1584 62.3% 37.8% 1139 81.3%
Niles 1218 1544 25.7% 68.5% 1108 83.0%
L’anse 1199 1389 25.0% 30.8% 1135 70.8%
Coldwater 1196 1533 28.6% 37.7% 1074 76.4%
Ludington 1184 1227 20.7% 38.6% 1171 87.4%
Gladwin 1176 1845 42.4% 37.3% 1006 n/a
Newberry 1172 1473 38.2% n/a 1092 84.6%
Adrian 1163 1570 31.3% 45.4% 1035 80.2%
Iron River 1161 1382 n/a n/a 1113 n/a
Petoskey 1160 1404 23.7% 76.1% 1083 82.3%
Cadillac 1148 1341 25.2% 34.4% 1081 75.0%
Grosse Pointe 1146 1184 16.3% 60.8% 1131 77.4%
Manistee 1140 1250 12.1% 30.1% 1108 78.2%
Clare 1138 1591 27.2% 53.1% 997 80.7%
Standish 1131 1501 46.6% 27.3% 1024 62.2%
Reed City 1128 1377 26.2% 54.9% 1053 n/a
St. Joseph 1122 1634 28.6% 60.4% 956 78.4%
Iron Mountain 1116 1308 24.4% 38.8% 1052 n/a
Sandusky 1108 1318 51.9% 46.2% 1042 n/a
Mount Pleasant 1108 1351 15.6% 41.7% 1018 66.9%
Sault Ste Marie 1092 1185 13.5% 38.7% 1062 71.6%
Laurium 1090 1168 24.6% 36.2% 1062 n/a
Grayling 1089 1354 29.5% 46.8% 1031 82.1%
Caro 1085 1133 22.7% 37.0% 1071 77.8%
Manistique 1079 1162 22.8% 31.4% 1055 n/a
Alma 1075 1319 35.6% 47.9% 990 76.1%
Escanaba 1072 1306 32.6% 38.9% 994 72.4%
Berrien Center 1069 1607 n/a n/a 862 n/a
Rochester 1064 1148 17.9% 68.6% 1035 70.3%
Ontonagon 1062 1195 n/a n/a 1025 n/a
Flint 1062 1148 27.3% 46.4% 1036 83.1%
Paw Paw 1056 1334 16.7% 68.6% 953 84.8%
Harbor Beach 1056 1584 43.6% n/a 872 n/a
Pontiac 1051 1204 26.7% 50.3% 1001 78.5%
Cass City 1047 1151 22.7% n/a 1014 n/a
Albion 1045 1087 29.7% 50.0% 1033 n/a
Tawas City 1044 1384 38.4% 40.0% 973 76.8%
Deckerville 1033 1300 n/a n/a 947 n/a
Ishpeming 1025 1229 40.8% 52.4% 957 n/a
Big Rapids 1024 1364 24.6% 47.2% 921 80.8%
Bay City 1023 1156 20.6% 58.7% 984 72.0%
Tecumseh 1018 1165 26.3% 36.1% 968 89.3%
Port Huron 1018 1140 21.5% 58.8% 974 78.0%
Milford 1002 1088 21.8% 64.8% 972 79.3%
Carson City 1002 1035 45.5% 45.7% 991 n/a
Ironwood 999 1136 n/a n/a 965 n/a
Troy 996 1080 17.6% 64.5% 968 74.0%
Alpena 993 1196 35.3% 18.0% 933 78.3%
Monroe 991 1078 33.3% 61.7% 964 81.0%
Royal Oak 988 1002 14.6% 70.8% 983 74.6%
Crystal Falls 985 1339 n/a n/a 900 n/a
Hastings 981 1229 21.0% 50.3% 889 81.3%
St. Johns 980 1211 37.5% 65.5% 895 74.7%
Mount Clemens 979 1108 20.6% 61.5% 933 74.2%
Traverse City 974 1082 17.1% 51.4% 937 72.3%
Saginaw 963 1068 21.4% 49.9% 931 76.3%
Hancock 963 1011 18.3% 45.6% 944 n/a
Owosso 963 1250 31.3% 60.3% 871 80.4%
Charlevoix 947 1111 28.0% 64.2% 891 77.6%
Kalamazoo 938 1051 13.7% 62.9% 900 81.4%
Marshall 931 988 36.8% 52.6% 910 83.7%
Jackson 930 1108 25.8% 74.6% 867 81.1%
Three Rivers 930 1031 22.2% 51.2% 896 n/a
South Haven 922 1140 50.0% 60.5% 853 83.6%
Munising 913 1190 n/a n/a 840 n/a
Lapeer 905 1038 32.7% 41.9% 862 81.4%
St. Clair 885 1045 17.3% 40.0% 836 75.8%
Lakeview 874 1150 n/a n/a 793 n/a
Warren 873 928 17.4% 57.6% 854 75.4%
Battle Creek 872 853 15.3% 63.3% 878 77.2%
Farmington Hills 863 851 16.4% 59.4% 867 73.4%
Lansing 852 987 22.8% 60.6% 808 79.4%
Frankfort 844 790 n/a n/a 857 n/a
Midland 838 992 16.8% 51.8% 785 77.7%
Marquette 831 939 23.1% 56.4% 802 78.2%
Charlotte 831 945 46.6% 46.0% 791 76.5%
Trenton 822 851 31.0% 46.8% 812 72.4%
Garden City 821 922 27.1% 42.3% 784 82.3%
Howell 814 786 18.2% 60.3% 828 80.3%
Livonia 806 803 18.7% 50.4% 806 78.7%
Zeeland 798 976 n/a n/a 703 n/a
Wyandotte 796 811 27.9% 45.0% 791 77.3%
Dearborn 789 842 22.0% 37.4% 770 77.3%
Ionia 780 965 n/a 40.9% 714 n/a
Northport 778 789 n/a n/a 776 n/a
Holland 765 824 10.6% 68.2% 742 78.5%
Grand Rapids 759 853 16.8% 67.4% 722 74.3%
Allegan 744 765 18.9% 69.0% 736 n/a
Taylor 739 665 26.5% 43.7% 763 82.6%
Grand Haven 732 771 8.2% 66.7% 717 80.5%
Madison Heights 728 724 22.0% 59.0% 729 66.2%
Fremont 727 781 17.8% 48.1% 707 66.7%
Detroit 712 575 16.1% 43.0% 756 69.4%
Wayne 687 633 25.0% 40.2% 704 77.7%
Muskegon 679 711 14.0% 52.7% 668 79.0%
Greenville 658 785 26.9% 60.6% 610 n/a
Chelsea 644 695 14.9% 70.6% 624 67.9%
Southfield 583 518 15.4% 63.8% 602 74.3%
Ann Arbor 553 483 15.7% 63.4% 583 77.0%
Saline 538 494 13.9% 62.1% 558 76.0%
TOTAL 896 972 21.9% 54.9% 870 77.7%

7 While there is likely an undercounting of antibiotic prescriptions due to prescriptions that cost less than the co-payment and prescriptions filled under $4 prescription programs, the results should not be substantially affected. These results are consistent with health plan results from 2005, before $4 prescription programs had a substantial effect on the market. Prescriptions are also not counted if they are written by a physician but never filled by the patient.

8 Butler, C.C., Hood, K., Verheij, T., Little, P., Melbye, H., Nuttall, J., Kelly, M.J., et al. (2009). Variation in antibiotic prescribing and its impact on recovery in patients with acute cough in primary care: prospective study in 13 countries. BMJ, 338(jun23 2), b2242–b2242. doi:10.1136/bmj.b2242

Prescribing Practices and Variation

Prescribing antibiotics for viral infections, which do not respond to antibiotics and nearly always get better on their own, is a driver of overall antibiotic prescribing rates. One study found that antibiotic prescribing for colds, upper respiratory infections, and bronchitis accounts for nearly one third of antibiotics prescribed in the outpatient setting.9

To quantify the extent to which inappropriate antibiotic prescribing drives variation in overall prescribing rates, we examined the association between measures of appropriate prescribing and overall prescription rates. Our measures of appropriate prescribing are based on measures used in the Healthcare Effectiveness Data and Information Set (HEDIS), a tool used by health plans to measure the effectiveness of healthcare.10

The first measure is the percentage of children with upper respiratory infections (URI) that are given antibiotics. Upper respiratory infections involve the nose, sinuses, throat, and trachea, with the most common example being the common cold. Overall in 2009, 21.9 percent of BCBSM covered children diagnosed with URI were prescribed antibiotics. This percentage excludes children who were prescribed antibiotics for reasons other than the URI, such as ear infections or strep throat. This rate is a decrease from the 44 percent of children who received antibiotics for URIs found in a national study in 1992, but there is still substantial room for improvement, since antibiotics are not found to improve outcomes in URIs in children.

There is a correlation between the percentage of children given antibiotics for URIs and the overall pediatric antibiotic prescribing rate in a geographic region. Figure 9 shows the relationship between those two measures. Regions with a higher overall antibiotic use rate for children also had a higher percentage of antibiotics used for conditions with a viral diagnosis. Of the variation in overall pediatric antibiotic prescribing rates, 31.4 percent is related to variation in prescribing rates for URI. In other words, it appears that high use regions of the state have a higher use, at least in part, due to a higher inappropriate use of antibiotics.

Figure IB6:9
Percent of Children Prescribed Antibiotics for Upper Respiratory Infection by Pediatric Prescribing Rate, BCBSM, 2009

figure-9

Another measure of appropriateness in antibiotic prescribing for children is whether children who received antibiotics for pharyngitis (sore throat) also received a test to confirm the infection was bacterial. Overall, 56.3 percent of children received the appropriate test when given antibiotics for a sore throat. Appropriate testing for pharangytis is related to overall antibiotic prescribing. That is, places with high rates of testing to confirm bacterial infection also had lower rates of antibiotic prescribing. This relationship is shown in Figure 10. Of the overall variation in pediatric antibiotic prescribing, 12.1 percent is related to testing patterns for pharyngitis. Regions of the state with higher use of antibiotics were also regions with lower rates of testing for the presence of bacterial infection.

Figure IB6:10
Percent of Children with Pharyngitis Given Appropriate Testing by Pediatric Prescribing Rate, BCBSM, 2009

figure-10

For adults, a measure of appropriateness was the percentage of adults diagnosed with bronchitis who were not given antibiotics. Like URI, most cases of bronchitis are viral and improve with appropriate non-antibiotic treatment. Prescribing rates for BCBSM adults with bronchitis in 2009 were very high—77.2 percent received a prescription for antibiotics. Although rates were high throughout the state, there was a statistically significant correlation between the rates of prescribing antibiotics for bronchitis and those regions with high overall use rates. That is, regions with the highest antibiotic dispensing for bronchitis also had the highest antibiotic dispensing overall. Of the variation in overall use rates, 8.8 percent is related to prescribing antibiotics for bronchitis (Figure 11).

Figure IB6:11
Percent of Adults Prescribed Antibiotics for Bronchitis by Adult Prescribing Rate, BCBSM, 2009

figure-11

9 Gonzales, R., Steiner, J.F., & Sande, M.A. (1997). Antibiotic Prescribing for Adults With Colds, Upper Respiratory Tract Infections, and Bronchitis by Ambulatory Care Physicians. JAMA: The Journal of the American Medical Association, 278 (11), 901 -904. doi:10.1001/ jama.1997.03550110039033

10 HEDIS measures the percentage of children with URI and percentage of adults with bronchitis not given antibiotics. Our measures report the inverse—the percentage of with those conditions who are given antibiotics.

Conclusion

Efforts to educate providers and patients, especially for pediatric providers and patients, have resulted in overall decreased use of antibiotics for viral infections. High rates of inappropriate antibiotic prescribing occur in some parts of Michigan, particularly outside of southeast Michigan. Of particular concern are the lack of testing for presence of a bacterial infection in children prior to prescribing an antibiotic, the continuing high use rates of antibiotics for viral infections in both children and adults, and the relatively high use of broad spectrum antibiotics among the adult population.

A number of efforts in Michigan have focused on reducing the inappropriate use of antibiotics. Most notably, the Michigan Antibiotic Resistance Reduction Coalition has had a number of successes in reducing inappropriate use over time. Overuse of antibiotics continues to be a major health problem in Michigan and nationally. Further efforts to reduce inappropriate use are essential for safeguarding our health and preserving the effectiveness of antibiotics.

 

Suggested citation: Kofke-Egger, Heather, Udow-Phillips, Marianne. Antibiotic Prescribing and Use. February 2011. Center for Healthcare Research & Transformation. Ann Arbor, MI.