McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 8  Anti-infective agents

Preventing resistance Because the emergence of resistant strains of microbes is a serious public health problem that continues to grow, healthcare providers must work together to prevent the emergence of resistant pathogens. Exposure to an anti- microbial agent leads to the development of resistance, so it is important to limit the use of antimicrobial agents to the treatment of specific pathogens known to be sen- sitive to the drug being used. Drug dosing is important in preventing the develop­ ment of resistance. Doses should be high enough and the duration of drug therapy should be long enough to eradicate even slightly resistant microorganisms. The recommended dosage for a specific anti-infective agent takes this issue into account. Around-the-clock dosing eliminates the peaks and valleys in drug concentration and helps to maintain a constant therapeutic level to prevent the emergence of resistant microbes during times of low concentration. The duration of drug use is critical to ensure that the microbes are completely, not partially, eliminated and are not given the chance to grow and develop resistant strains. It has proved to be difficult to convince people who are taking anti-infective drugs that the timing of doses and the length of time they continue to take the drug are important. Many people stop taking a drug once they start to feel better and then keep the remaining pills to treat themselves at some time in the future when they do not feel well. This practice favours the emergence of resistant strains. Box 8.4 gives tips on teaching about this. Healthcare providers should also be cautious about the indiscriminate use of anti-infectives. Antibiotics are not effective in the treatment of viral infections or illnesses such as the common cold. However, many people seek prescriptions for these drugs when they visit practitioners because they are convinced that they need to take something to feel better. Healthcare providers who prescribe anti-infectives without knowing the caus- ative organism and which drugs might be appropriate Using anti-infective agents When teaching people who are prescribed an anti- infective agent, it is important to always include some general points: • This drug is prescribed for treating the particular infection that you have now. Do not use this drug to treat other infections. • This drug needs to be taken as prescribed—for the correct number of times each day and for the full number of days. Do not stop taking the drug if you start feeling better.You need to take the drug for the full number of treatment days to ensure that the infection has been destroyed. Individual and family teaching BOX 8.4

are promoting the emergence of resistant strains of microbes. With many serious illnesses, including pneu- monias for which the causative organism is suspected, antibiotic therapy may be started as soon as a sample of the bacteria, or culture , is taken and before the results are known. Healthcare providers also tend to try newly introduced, more powerful drugs when a more estab- lished drug may be just as effective. Use of a powerful drug in this way leads to the rapid emergence of resistant strains to that drug, perhaps limiting its potential use- fulness when it might be truly necessary. ■■ The goal of anti-infective therapy is the reduction of the invading organisms to a point at which the human immune response can take care of the infection. ■■ Anti-infectives can act to destroy an infective pathogen (bactericidal) or to prevent the pathogen from reproducing (bacteriostatic). ■■ Anti-infectives can have a small group of pathogens against which they are effective (narrow spectrum), or they can be effective against many pathogens (broad spectrum). Using anti-infective agents Anti-infective agents are used to treat systemic infec- tions and sometimes as a means of prophylaxis (to prevent infections before they occur). Treatment of systemic infections Many infections that once led to lengthy, organ-damaging or even fatal illnesses are now managed quickly and effi- ciently with the use of systemic anti-infective agents. Before the introduction of penicillin to treat strepto­ coccal infections, many people developed rheumatic fever with serious cardiac complications. Today, rheu- matic fever and the resultant cardiac valve defects are seldom seen. Several factors should be considered before beginning one of these chemotherapeutic regimens to ensure that the person obtains the greatest benefit possible with the fewest adverse effects. These factors include identification of the correct pathogen and selec- tion of a drug that is most likely to (1) cause the least complications for that person and (2) be most effective Identification of the infecting pathogen is done by cul- turing a tissue sample from the infected area. Bacterial cultures are performed in a laboratory, in which a swab of infected tissue is allowed to grow on an agar plate. Staining techniques and microscopic examination are used to identify the offending bacterium. When investi­ gators search for parasitic sources of infection, they against the pathogen involved. Identification of the pathogen KEY POINTS KEY POINTS