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ANTI-INFECTIVE AGENTS

ANTI-INFECTIVE AGENTS. Chapter 8. Anti-infective agents. Anti-infective agents are drugs designed to target foreign organisms that have invaded and infected the body of a human host.

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ANTI-INFECTIVE AGENTS

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  1. ANTI-INFECTIVE AGENTS Chapter 8

  2. Anti-infective agents • Anti-infective agents are drugs designed to target foreign organisms that have invaded and infected the body of a human host.

  3. Although anti-infective agents target foreign organisms infecting the body of a human host, they do not possess selective toxicity, which is the ability to affect certain proteins or enzyme systems used only by the infecting organism but not by human cells. • Because all living cells are somewhat similar, however, no anti-infective drug has yet been developed that does not affect the host.

  4. Anti-Infective Activity • The anti-infectives used today vary in their spectrum of activity; that is, they vary in their effectiveness against invading organisms. • narrow spectrum of activity. • broad spectrum of activity.

  5. Some anti-infectives are so active against the infective microorganisms that they actually cause the death of the cells they affect. These drugs are said to be bactericidal. • Some anti-infectives are not as aggressive against invading organisms; they interfere with the ability of the cells to reproduce or divide. These drugs are said to be bacteriostatic.

  6. Human Immune Response • if a person is immunocompromised for any reason It is difficult to treat any infections in such patients for two reasons: • (1) Anti-infective drugs cannot totally eliminate the pathogen without causing severe toxicity in the host,and • (2) these patients do not have the immune response in place to deal with even a few invading organisms.

  7. Resistance • Resistance can be natural or acquired, and refers to the ability over time to adapt to an anti-infective drug and produce cells that are no longer affected by a particular drug.

  8. Acquiring Resistance • Microorganisms develop resistance in a number of ways,includingthe following: 1-• Producing an enzyme that deactivates the antimicrobial drug. • For example, some strains of bacteria that were once controlled by penicillin now produce an enzyme called penicillinase,

  9. …Acquiring Resistance 2-• Changing cellular permeability to prevent the drug from entering the cell or altering transport systems to exclude the drug from active transport into the cell. 3-• Altering binding sites on the membranes or ribosomes,whichthen no longer accept the drug. 4-• Producing a chemical that acts as an antagonist to the drug.

  10. Preventing Resistance • Drug dosing is important in preventing the development of resistance. • Doses should be high enough and the duration of drug therapy should be long enough to eradicate even slightly resistant microorganisms. • Around-the-clock dosing. • Many people stop taking a drug once they start to feel better,…

  11. …Preventing Resistance • Antibiotics are not effective in the treatment of viral infections. • culture

  12. Using Anti-Infective Agents • Anti-infective agents are used to treat systemic infections • and sometimes as a means of prophylaxis.

  13. Identification of the Pathogen • Identification of the infecting pathogen is done by culturing a tissue sample from the infected area. • Sensitivity of the Pathogen: • It is necessary to perform sensitivity testing on the cultured microbes to evaluate bacteria and determine which drugs are capable of controlling the particular microorganism.

  14. Combination Therapy • Combination therapy may be used for several reasons: • 1- The health care provider may be encouraged to use a smaller dose of each drug, leading to fewer adverse effects but still having a therapeutic impact on the pathogen. • 2- Some drugs are synergistic, which means that they are more powerful when given in combination.

  15. …Combination Therapy • 3- • Many microbial infections are caused by more than one organism, and each pathogen may react to a different anti-infective agent. • 4- • Sometimes, the combined effects of the different drugs delay the emergence of resistant strains. This is important in the treatment of tuberculosis (a mycobacterial infection), malaria (a protozoal infection), HIV infection (a viral infection), and some bacterial infections. • Resistant strains may be more likely to emerge when fixed combinations are used over time; however, this may be prevented by individualizing the combination.

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