Antimicrobial Drugs

Antimicrobial drugs include numerous classes of drugs that are used in everyday practice all around the world in treatment or prophylaxis of infections caused by a variety of microorganisms. Therefore, antimicrobial drugs comprise antibacterial, antifungal, antiparasitic and antiviral agents, and that depends on the spectrum of activity of the antimicrobial agent. The major feature of these drugs is their selective toxicity, meaning they primarily target a specific microorganism while host cells remain relatively intact. Resistance of microorganisms to the antimicrobials is rising and represents threatening problem so antimicrobial drugs should be used prudently and with caution. Antibacterial agents are generally classified according to their target site and then grouped based on their chemical structure. Furthermore, antifungal agents are more and more important due to increased numbers of immunocompromised hosts and high mortality and morbidity of fungal infection. Most important classes such as polyenes, azoles and ehinocandines as well as other anifungal drugs are described. Antiparasitic agents are also very important because parasites are causing for a large number of infections in humans. Treatment of these infections is complicated by the fact that parasites are eukaryotic organisms and therefore resemble the human host regarding cell structure and metabolism. This is the reason why antiparasitic therapy is rather limited, complex and has numerous adverse effects. Generally, antiparasitic drugs are divided into two large groups: antiprotozoal and antihelminthic agents. Antiviral agents are lately used more often due to many immunocompromised patients that are prone to this kind of infection. Antiviral drugs can be divided depending on the site of action in the viral life cycle or regarding on the virus against which they are effective. In this chapter, we will discuss mechanisms of action, spectrum of activity, resistance mechanisms, pharmacokinetics, most important side effects and drug interactions for all above-mentioned classes of antimicrobial drugs.