This chapter and the next two address drugs used to treat infections caused by pathogenic microorganisms and parasites. Microorganisms such as bacteria, viruses, and protozoa, as well as larger multicellular parasites, frequently invade human tissues and are responsible for various afflictions, ranging from mild and annoying symptoms to life-threatening diseases. Often, the body's natural defense mechanisms are unable to deal with these pathogenic invaders, and pharmacological treatment is essential in resolving infections and promoting recovery. The development of drugs to treat infection represent one of the most significant advances in medical history, and these agents are among the most important and widely used pharmacological agents throughout the world.
Drugs used to treat infectious diseases share a common goal of selective toxicity, meaning they must selectively kill or attenuate the growth of the pathogenic organism without causing excessive damage to the host (human) cells. In some cases, the pathogenic organism may have some distinctive structural or biochemical feature that allows the drug to selectively attack the invading cell. For instance, drugs that capitalize on certain differences in membrane structure, protein synthesis, or other unique aspects of cellular metabolism in the pathogenic organism will be effective and safe anti-infectious agents. Of course, selective toxicity is a relative term, because all of the drugs discussed in the following chapters exert some adverse effects on human tissues. However, these drugs generally impair function much more in the pathogenic organism than in human tissues.
Several other general terms are also used to describe the drugs. Agents used against small, unicellular organisms (e.g., bacteria, viruses) are often referred to as antimicrobial drugs. Another common term for antimicrobial agents is antibiotics, indicating that these substances are used to kill other living organisms (i.e., anti-bios, or life). To avoid confusion, this text classifies and identifies the antimicrobial agents according to the primary type of infectious organism they are used to treat—that is, whether they are antibacterial, antiviral, antifungal, and so on. This chapter focuses on drugs that treat bacterial infections. Drugs for treating and preventing viral infections are presented in Chapter 34, followed by the pharmacological management of other parasitic infections (i.e., antifungal, antiprotozoal, and anthelmintic drugs) in Chapter 35.
Because infectious disease represents one of the most common forms of illness, many patients undergoing physical rehabilitation may be taking one or more of these drugs. Physical therapists and occupational therapists will undoubtedly deal with patients on a routine basis who are undergoing chemotherapy for infectious disease. Patients can, for example, develop infections following joint replacements and other surgeries. These infections must be treated effectively to allow full recovery and enable the patient to progress during physical rehabilitation. Infections in the respiratory tract, kidneys, gastrointestinal (GI) tract, and other organs and tissues must also be resolved so that the patient can fully engage in exercise and other rehabilitation interventions.