Part 6 Antimycobacterials & Other Antibiotics

Anti-Mycobacterials Overview

Introduction to Mycobacteria

• Mycobacteria are a group of bacteria responsible for diseases such as tuberculosis and leprosy.

• They possess mycolic acid, which makes them resistant to many disinfectants and allows survival in harsh environments.

Specific Mycobacterial Diseases

• Tuberculosis: Caused by Mycobacterium tuberculosis, it is a significant public health concern.

• Leprosy: Also known as Hansen's disease, caused by Mycobacterium leprae, characterized by disfiguring skin lesions and respiratory tract damage.

• AIDS-related infections: Mycobacterium avium can affect immunocompromised patients, particularly those with AIDS.

Treatment Protocols for Tuberculosis

Anti-Tuberculosis Drugs

• Treatment duration ranges from six months to two years due to the slow growth rate of mycobacteria; combination therapy is essential to prevent resistance.

• First-line drugs include Rifampin, Isoniazid (INH), Pyrazinamide, and Ethambutol (RIPE). These are crucial in community health nursing contexts.

Second-Line Treatments

• Secondary treatments may involve other antibiotic classes like aminoglycosides or fluoroquinolones when first-line therapies fail or resistance develops.

Leprosy Treatment Insights

Leprostatic Drugs

• The mainstay treatment for leprosy includes Dapsone, which inhibits folate synthesis similar to sulfonamides. This drug is also used for treating Pneumocystis pneumonia in AIDS patients.

• Thalidomide is utilized for treating erythema nodosum leprosum, an inflammatory condition related to immune reactions post-leprosy treatment.

Pharmacological Considerations

Drug Mechanisms and Effects

• Isoniazid specifically targets the mycolic acid layer of bacteria; all anti-tuberculosis drugs should be used in combination to reduce resistance emergence during various bacterial life stages.

Contraindications and Adverse Effects

• Common contraindications include known allergies, hepatic/renal failure, severe CNS dysfunction, and pregnancy considerations where Rifampin/Isoniazid/Ethambutol combinations are deemed safest.

Patient Education on Side Effects

Adverse Reactions

• Patients may experience CNS effects like dizziness or hallucinations; gastrointestinal issues such as nausea or abdominal pain are also common side effects associated with these medications.

Body Fluid Discoloration

• Rifampin can cause discoloration of body fluids (urine/sweat/tears), necessitating patient education about potential orange staining on clothing and contact lenses.

Drug Interactions and Toxicity Risks

Interaction Concerns

• Certain drug interactions can lead to toxic liver reactions or decreased effectiveness when combined with agents like beta-blockers or anticonvulsants alongside rifampin derivatives like rifabutin/rifapentine.

Ototoxicity Risks

• Streptomycin poses risks of ototoxicity and nephrotoxicity; careful monitoring is required during its use alongside other antibiotics that may have similar toxicity profiles such as ketolides or macrolides used for severe infections.

Macrolides Overview

Indications for Use

Azithromycin and Antibiotic Administration

Azithromycin Dosage and Absorption

• Azithromycin has a half-life of 6 to 8 hours, typically prescribed once daily or every other day based on the doctor's order.

• Administering azithromycin on an empty stomach enhances absorption; food can decrease its effectiveness.

Tetracyclines and Macrolides

• Tetracyclines should be taken with a full glass of water, one hour before or two to three hours after meals for optimal absorption.

• Macrolides like erythromycin also require administration on an empty stomach for better efficacy.

Oxazolidinones Overview

• Oxazolidinones are effective against vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA).

Adverse Effects of Antibiotics

• Common side effects include CNS issues such as headaches, insomnia, dizziness, gastrointestinal disturbances like nausea and diarrhea, and potential for pseudomembranous colitis.

• Caution is advised when combining oxazolidinones with drugs that increase blood pressure due to risks of hypertension and bleeding.

Drug Interactions with Food

• Patients taking oxazolidinones should avoid tyramine-containing foods (e.g., aged cheese, red wine), which can lead to severe hypertension.

New Antibiotics: Tigecycline

Tigecycline Usage

• Tigecycline is a new class antibiotic approved for complicated skin infections and intra-abdominal infections; caution is needed in patients allergic to tetracycline.

Clavulanic Acid Role

• Clavulanic acid protects certain beta-lactam antibiotics from breakdown by penicillinase enzymes, enhancing their effectiveness against resistant bacteria.

Vancomycin: Mechanism and Risks

Vancomycin Effectiveness

• Vancomycin prevents bacterial wall synthesis; it is effective only against gram-positive bacteria including MRSA.

Adverse Effects of Vancomycin

• Nephrotoxicity is the most significant adverse effect associated with vancomycin use. Monitoring renal function is crucial during treatment.

Monitoring During Vancomycin Therapy

Red Man Syndrome

• Rapid administration of vancomycin can cause Red Man Syndrome characterized by hypotension and rash; slow IV administration helps mitigate this risk.

Therapeutic Levels