Chapter 21: Drug Therapy With Macrolides and Miscellaneous Anti-infective Agents

Macrolide Antibacterials

Macrolides are a class of antibiotics widely used in clinical practice for their effectiveness against various bacterial infections. Their mechanism of action and pharmacokinetics make them suitable for treating both common and specialized infections.

• Erythromycin is the prototype macrolide, distributed widely into body tissues and fluids.

• Macrolides can be bacteriostatic (inhibit bacterial growth) or bactericidal (kill bacteria), depending on drug concentration in infected tissues.

• They are particularly effective against gram-positive cocci.

Example: Erythromycin is used to treat respiratory tract infections caused by Streptococcus pneumoniae.

Pharmacokinetics and Clinical Considerations

Understanding the pharmacokinetics and clinical considerations is essential for safe and effective use of macrolides.

• Action: Inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit.

• Use: Treat respiratory tract and soft tissue infections, and as a substitute for penicillin in patients with hypersensitivity.

• Hepatic Impairment: Caution is required as macrolides are metabolized in the liver.

• Critical Illness: Adjustments may be needed for patients with severe illness.

• Adverse Effects: Gastrointestinal disturbances, hepatotoxicity, and potential for drug interactions.

• Contraindications: Hypersensitivity to macrolides, preexisting liver disease, and myasthenia gravis.

Example: Azithromycin is preferred for its longer half-life and fewer gastrointestinal side effects compared to erythromycin.

Indications for Macrolide Use

Macrolides are indicated for a variety of infections, especially when other antibiotics are contraindicated.

• Respiratory tract and soft tissue infections

• Penicillin substitute for patients with hypersensitivity

• Prophylaxis: Rheumatic fever, gonorrhea, syphilis, pertussis, and chlamydial conjunctivitis in newborns

• Treatment for other infections: Legionnaires disease, genitourinary (GU) infections, bacterial sinusitis

Example: Macrolides are used to prevent pertussis in exposed newborns.

Other Drugs in the Macrolide Class

Several macrolides are available, each with unique properties and clinical uses.

• Azithromycin

• Clarithromycin

• Fidaxomicin

Example: Azithromycin is commonly used for community-acquired pneumonia.

Contraindications for Macrolide Use

Contraindications must be considered to prevent adverse outcomes.

• Hypersensitivities

• Preexisting liver disease

• Myasthenia gravis

Example: Macrolides should be avoided in patients with severe hepatic dysfunction.

Miscellaneous Anti-infective Agents

In addition to macrolides, several other anti-infective agents are used for specific infections and resistant organisms.

• Chloramphenicol

• Clindamycin

• Dalbavancin

• Daptomycin

• Linezolid

• Metronidazole

• Oritavancin

• Quinupristin–Dalfopristin

• Rifaximin

• Tedizolid

• Telavancin

• Tigecycline

• Vancomycin

Example: Vancomycin is used for methicillin-resistant Staphylococcus aureus (MRSA) infections.

Principles of Therapy

Effective antimicrobial therapy relies on proper selection and monitoring.

• Culture and susceptibility reports are essential to determine resistance before starting therapy.

• Most agents have relatively narrow spectra of activity.

• Preventing toxicity is vital, especially in vulnerable populations.

Example: Susceptibility testing guides the choice of antibiotics for resistant infections.

Nursing Implications

Nurses play a critical role in ensuring safe and effective antimicrobial therapy.

• Preventing interactions: Monitor for drug-drug interactions.

• Administering the medication: Follow proper dosing and administration guidelines.

• Assessing for therapeutic effects: Monitor patient response to therapy.

• Assessing for adverse effects: Watch for signs of toxicity or allergic reactions.

• Patient teaching: Educate patients about medication adherence and potential side effects.

Example: Patients should be instructed to complete the full course of antibiotics to prevent resistance.

Table: Macrolide Antibiotics - Comparison

Additional info: Table entries inferred from standard clinical uses and adverse effects of macrolides.