Copyright © 2015 Cengage Learning® 1 Chapter 17 Anti-Infective Drugs

Copyright © 2015 Cengage Learning® 1Copyright © 2015 Cengage Learning®

Chapter 17Anti-Infective Drugs

Copyright © 2015 Cengage Learning® 2

Introduction• Treatment of infection

– Complicated by the great variety of medications available and their differing modes of action

– First step: identify the causative organism and specific medication to which it is sensitive• Culture and sensitivity (C&S) tests


Resistance• Organisms may build up resistance to

drugs and are therefore, no longer effective because of: – Frequent use– Incomplete treatment

• Anti-infective resistance is caused by many factors– Complex strategies needed to combat the

problem


Resistance (cont’d.)• Selection of anti-infective drugs

– Infection site– Status of hepatic and/or renal function– Patient age – Pregnancy or lactation – Likelihood of organisms developing resistance– Known allergy to the anti-infective drug


Adverse Reactions• Categories

– Allergic hypersensitivity• Over-response of the body to a specific substance

– Direct toxicity• Results in tissue damage

– Indirect toxicity or superinfection• Manifested as a new infection due to absence of

normal flora in the intestines or mucous membranes


Vaccines/Immunizations • Centers for Disease Control and

Prevention (CDC) – Currently recommends routine vaccination

• Prevent 17 vaccine-preventable diseases that occur in infants, children, adolescents, or adults

• Information regarding vaccines and immunizations changes from time to time and requirements may vary by state, territory, or country


Aminoglycosides• Treats many infections caused by:

– Gram-negative bacteria (e.g., Escherichia coli and Pseudomonas)

– Gram-positive bacteria (e.g., Staphylococcus aureus)

• Effective in short-term treatment of many serious infections – Septicemia (e.g., bacteria in bloodstream

causing low blood pressure) when less toxic drugs are ineffective or contraindicated


Cephalosporins• Semisynthetic beta-lactam antibiotic

derivatives produced by a fungus– Related to penicillins

• Some patients allergic to penicillin are also allergic to cephalosporins

• Classified as first, second, third, or fourth, or fifth generation– According to organisms susceptible to their

activity


Macrolides• Treats many infections of the respiratory

tract, skin conditions, or for some sexually transmitted infections– Considered among the least toxic antibiotics

• Preferred for treating susceptible organisms under conditions in which more toxic antibiotics might be dangerous


Penicillins• Beta-lactam antibiotics produced from

certain species of a fungus– Treats many streptococcal and some

staphylococcal and meningococcal infections– Drug of choice for treatment of syphilis – Used prophylactically to prevent recurrences

of rheumatic fever


Carbapenems• Belong to the beta-lactam class of

antibiotics – Have a very broad spectrum of activity

against gram-negative and gram-positive organisms

– Primary treatments include pneumonia, febrile neutropenia, intra-abdominal infections, diabetic foot infections, and significant polymicrobial infections


Quinolones• For adult treatment of some infections of

the urinary tract, sinuses, lower respiratory tract, GI tract, skin, bones, and joints, and in treating gonorrhea– Some organisms are showing increased

resistance – Reserve for infections that require therapy

with a fluoroquinolone


Tetracyclines• Broad-spectrum antibiotics

– Treats infections caused by rickettsia, chlamydia, or some uncommon bacteria

– Some organisms are showing increasing resistance

– Use only when other antibiotics are ineffective or contraindicated


Antifungals• Treat specific susceptible fungal disease

– Medications are quite different in action and purpose

• Amphotericin B – Administered IV for the treatment of severe

systemic and potentially fatal infections caused by susceptible fungi, including Candida


Antifungals (cont’d.)• Fluconazole

– Works against many fungal pathogens, including most Candida, without the serious toxicity of amphotericin B

• Micafungin (Mycamine)– Given IV– Provides new treatment options against

Candida and Aspergillus species


Antifungals (cont’d.)• Nystatin

– Structurally related to Amphotericin B – Orally treats oral cavity candidiasis– Also used as a fungicide in the topical

treatment of skin and mucous membranes


Antituberculosis Agents• Tuberculosis (TB)

– Caused by a bacterium called Mycobacterium tuberculosis, which primarily attacks the lungs

• Antituberculosis agents are administered for two purposes– To treat latent or asymptomatic infection (no

evidence of clinical disease)– For treatment of active clinical tuberculosis

and to prevent relapse


Miscellaneous Anti-Infectives• Clindamycin

– Treats serious respiratory tract infections, septicemia, osteomyelitis, serious infections of the female pelvis caused by susceptible bacteria, and for Pneumocystis jirovecii pneumonia associated with AIDS

– Prophylactic use in dental procedures for penicillin-allergic patients

– May be a viable therapeutic option for community-acquired MRSA


Miscellaneous Anti-Infectives (cont’d.)

• Metronidazole (Flagyl) – Synthetic antibacterial and antiprotozoal

agent – Effective against protozoa – One of the most effective drugs against

anaerobic bacterial infections– Also useful in treating Crohn’s disease,

antibiotic-associated diarrhea, rosacea, and H. pylori infection


Miscellaneous Anti-Infectives (cont’d.)

• Vancomycin – Structurally unrelated to other available

antibiotics– IV vancomycin is used in the treatment of

potentially life-threatening infections caused by susceptible organisms


Agents for VRE• Linezolid (Zyvox)

– Indicated for gram-positive infections – Approved for the treatment of bacterial

pneumonia skin, skin structure infections, and MRSA and VRE infections

– Effective in treating diabetic foot infections– Administered by IV infusion or orally


Sulfonamides• Among the oldest anti-infectives

– Increasing resistance of many bacteria has decreased the clinical usefulness of these agents

• Used most effectively in combinations with other drugs– Example: sulfamethoxazole and trimethoprim– Resistance develops more slowly


Urinary Anti-Infectives• Urinary tract infection (UTI)

– Symptomatic inflammatory response from the presence of microorganisms in the urinary tract

– One of the most common bacterial infections for which patients seek treatment

– First-line urinary anti-infectives for empiric treatment of uncomplicated lower UTI are sulfamethoxazole-trimethoprim and nitrofurantoin


Antivirals• Acyclovir

– Primarily treats herpes simplex, herpes zoster (shingles), and varicella zoster (chickenpox) infections

• Neuraminidase inhibitors – Indicated for the treatment of uncomplicated

acute illness due to influenza types A and B


Antivirals (cont’d.)• Ribavirin

– Treats infants and young children with respiratory syncytial virus (RSV) infections via nasal and oral inhalation


Treatment of HIV/AIDS Infections• Highly specialized field

– Those actively practicing in that field must be updated frequently on the many new medications and frequently changing protocols

• Treatment of HIV infection – Consists of using highly active antiretroviral

therapy (HAART) combinations of three or more antiretroviral (ARV) agents


Treatment of HIV/AIDS Infections (cont’d.)

• Antiretroviral protease inhibitors (PIs)– Block the activity of the HIV enzyme essential

for viral replication late in the virus life cycle• Nucleoside reverse transcriptase inhibitors

(NRTIs)– Inhibit an enzyme responsible for viral

replication early in the virus life cycle



• Non-nucleoside reverse transcriptase inhibitors (NNRTIs)– Inhibit an enzyme responsible for viral

replication early in the viral life cycle• Fusion inhibitors (FIs)

– Block entry of HIV into cells, which may keep the virus from reproducing



• CCR5 antagonists – Block a co-receptor required for HIV entry into

human cells• Integrase inhibitor

– Raltegravir (Isentress): first ARV designed to slow the advancement of HIV infection by blocking the enzyme needed for viral replication


HIV Information and Resources• Sources of current recommendations for

clinical use of antiretrovirals (ARVs) – Department of Health and Human Services– Florida/Caribbean Aids Education and

Training Center– AETC National Resource Center Drug

Interactions– Johns Hopkins HIV Guide– National HIV Telephone Consultation Service– University of California, San Francisco

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Copyright © 2015 Cengage Learning® 1 Chapter 17 Anti-Infective Drugs