Appropriate Antimicrobial Prescribing: Approaches that Limit An

  • Since the introduction of antimicrobial agents, there has been an association between antibiotic use and the development of antimicrobial resistance. Antibiotic therapy eradicates not only pathogenic organisms but also the protective normal flora. This so-called “selective pressure” results in colonization with bacteria that are resistant to the original therapy. The result has been an increase over the past two decades in antibiotic resistance among common bacterial causes of outpatient infections. Several studies have demonstrated that a substantial portion of the antibiotics prescribed in the outpatient setting are given for viral illnesses or bacterial diseases where the benefit of antibacterial therapy is marginal. The reasons for prescribing antibiotics in these situations are related to medical and social factors. Physicians should be familiar with the clinical situations in which they should provide antibiotics and those in which they may safely be withheld. Physicians should understand the motivations of patients who are seeking antibiotics and provide education, empathy and alternative treatments.

    The development of antibiotic-resistant bacteria seems to be an inevitable consequence of using antimicrobial drugs. Antimicrobial resistance has increased since the introduction of antibiotics. Penicillin was first used in the early 1940s and by 1950, most Staphylococcus aureus organisms were resistant to the drug by virtue of elaboration of a penicillinase enzyme.

    The emergence of a resistant population of bacteria in a patient as a result of antibiotic use generally occurs through a process termed “selective pressure.” Studies using special culture techniques show that healthy persons normally harbor small numbers of bacteria that are intrinsically resistant to antibiotics. The larger numbers of antibiotic-susceptible organisms usually keep resistant bacteria in check. The use of any antibiotic eliminates organisms susceptible to that drug at the site of infection and at all sites in the body into which the drug penetrates in adequate concentrations. Selective pressure occurs when the administration of an antibiotic decreases the numbers of normal flora, allowing resistant bacteria to proliferate. Find more at the

    When antibiotics are prescribed to large numbers of persons in a population, resistant bacteria may become the predominant organisms in that community. This situation is occurring with respiratory-tract pathogens that were once universally susceptible to antibiotics. A national survey of clinically significant outpatient isolates of Streptococcus pneumoniae, the most common bacterial cause of most respiratory tract infections, gathered from 30 U.S. medical centers in 1994 and 1995, revealed that 23.6 percent of strains were not susceptible to penicillin. Intermediate resistance was detected in about 14.1 percent of isolates, while about 9.6 percent of strains demonstrated high-level resistance. A recent study in Iceland showed a direct correlation between the use of antibiotics and the prevalence of resistant S. pneumoniae strains.

    Appropriate prescribing of antibiotics may slow the rate at which resistance becomes widespread throughout the community. A study in Finland demonstrated that erythromycin resistance among group A streptococci decreased from 16.5 to 8.6 percent over a four-year period during a nationwide program relying on national guidelines to limit the use of erythromycin. Other studies in the United States show that decreased use of antibiotics for prophylaxis and treatment correlated with decreasing rates of colonization with resistant organisms.

    Inappropriate Antibiotic Use

    Despite the association between the increased use of antibiotics and the spread of resistant organisms in the community, antibiotic use in this country appears to be increasing. A national office-based study suggested an increase of 48 percent in antibiotic prescribing for children between 1980 and 1992. The use of antimicrobials is especially prevalent in the very young and the elderly. In one study, 37 and 70 percent of children, by three and six months of age respectively, had received at least one antibiotic prescription. The emergence of in vitro resistance in previously susceptible pathogens, such as S. pneumoniae in respiratory tract infections and Escherichia coli in urinary tract infections, has temporally coincided with the increase in antibiotic use.

    A good portion of antibiotic use appears to be for viral or spontaneously resolving bacterial infections. The Centers for Disease Control and Prevention (CDC) estimates that about 100 million courses of antibiotics are prescribed by office-based physicians each year, and that approximately one half of those prescriptions are unnecessary. Most antibiotic prescriptions in the ambulatory setting are for respiratory infections. Studies evaluating physicians' prescribing patterns have found that almost 50 percent of office visits for colds and upper respiratory tract infections (URIs), and 80 percent of visits for acute bronchitis are treated with antibacterial agents. This prescribing pattern persists despite the fact that antibacterial agents have no effect against a viral disease such as the common cold. Data from numerous studies show that antibacterial agents do not significantly shorten the duration of illness in acute bronchitis.

    Physicians continue to prescribe antibiotics despite acknowledging the association of antimicrobial use and bacterial resistance. In one study, 97 percent of surveyed physicians agreed that overuse of antibiotics is a major factor contributing to antimicrobial resistance. However, an evaluation of the practice patterns of these same physicians revealed continued prescribing of antimicrobials for viral illnesses. Other potential harms of indiscriminate antibiotic prescribing include allergic reactions, adverse reactions and drug-drug interactions.

    Reasons for Prescribing

    Patients want antibiotics, and physicians continue to prescribe them in situations where antibiotics may be withheld for many reasons. The act of prescribing an antibiotic has social and medical implications. From the patient's point of view, the prescribing of an antibiotic validates that the patient does have an illness, that a diagnosis has been made and that the illness is amenable to treatment. The fact that there is a “cure” for their problem reassures them that the illness is not serious.

    Patients are accustomed to receiving antibiotics for benign URIs and have come to believe, sometimes very strongly, that antibiotics demonstrate efficacy and are necessary for proper treatment of these illnesses. So convinced are patients of the efficacy of antibiotics that in one clinical trial of acute bronchitis, 60 percent of patients screened for the study refused to participate because they did not wish to be randomized to the placebo arm of the trial.

    The most common clinical factor causing patients to seek medical help for common infections is relief of bothersome symptoms. In one study, 90 percent of patients with URIs came to the physician's office because of a persistent cough. Another two thirds of patients complained of disturbed sleep, while nearly one half made an appointment at the urging of family and friends. Antibiotics have little effect on the rate of resolution of cough or disturbed sleep.

    Certain clinical features of disease may inappropriately influence physicians' treatment decisions. The presence of purulent nasal discharge is more likely to result in a physician's prescribing an antibiotic for a patient with acute bronchitis. However, the purulent nasal discharge does not adequately differentiate viral from bacterial etiologies and is not associated with a worse outcome.

    The presence of cough for more than three days may also trigger an antibiotic prescription. The natural history of acute bronchitis is such that many patients cough for two to three weeks as a result of bronchial hyperresponsiveness and not as a result of persistent infection. In the absence of chronic obstructive lung disease, fever and a smoking history are not indications for antibiotic therapy in patients with acute bronchitis. Physicians may prescribe antibiotics in the hope of preventing more serious superinfections, but a meta-analysis of studies on antibiotic use in URIs did not show an effect of antibiotics in decreasing the incidence or severity of subsequent disease.

    Physicians' prescribing patterns appear to be affected by nonclinical factors in up to one half of cases. In today's managed-care environment, physicians are pressed to see more patients in less time. They have insufficient time to educate patients about the ineffectiveness of antibiotics. Prescribing an antibiotic may be an effective way to conclude an office visit. Although some physicians believe that prescribing an antibiotic will decrease return office visits, up to one fourth of patients with URIs make a return visit within one month of the initial encounter regardless of the prescription of antibiotic agents.

    Although physicians often feel compelled to prescribe an antibiotic to satisfy patient demands, patient satisfaction surveys indicate that patients do not acknowledge putting such pressure on their physicians. One survey indicated that while 65 percent of patients expected to receive an antibiotic for treatment of a URI, there was no correlation between patient satisfaction and receipt of an antibiotic prescription. Instead, patient satisfaction correlated highest with the quality of the physician-patient interaction. Results from focus groups indicate that patients would be satisfied if an antibiotic was not prescribed as long as the physician explained the reasons for the decision to withhold antibiotics.

    Approach to the Patient

    The physician should take a well-reasoned, step-wise approach to a patient with an infection before prescribing an antibiotic. The first step is to make a tentative diagnosis based on data from the history and physical examination. Often, it is difficult to distinguish a bacterial from a viral illness by clinical features alone. Clinical and laboratory factors can be helpful in selecting subsets of patients more likely to have bacterial disease. More important than the actual microbiologic cause of the infection is knowledge of whether antibiotics will affect the course of the illness. For example, antibiotic therapy has little effect on the course of acute bronchitis caused by the bacterial pathogens Mycoplasma pneumoniae or Chlamydia pneumoniae.

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