Pharmacology of Metronidazole and Antibacterials

Study Notes

Metronidazole (Flagyl)

Functions as a bactericidal agent, effective against specific pathogens.
Used for protozoal infections and infections from obligate anaerobes, including C. difficile and intra-abdominal infections.
Also targets Helicobacter pylori, implicated in peptic ulcers.
Potential adverse effects include neurotoxicity, nephrotoxicity, allergic reactions, and superinfections.
Infusion site reactions may occur; careful monitoring for allergic and CNS side effects is essential.
Alcohol consumption leads to disulfiram reaction, causing severe nausea and vomiting.

Additional Antibacterial Drugs

Rifampin
- Broad-spectrum antibacterial primarily used for tuberculosis (TB) treatment.
- Sometimes utilized in conjunction with other drugs for certain meningitis cases, not as monotherapy.
Rifaximin
- Oral non-absorbable rifampin variant for treating traveler’s diarrhea.
- Common side effects include nausea, flatulence, and urgency in defecation.
Bacitracin
- Mostly used topically for bacterial infections; systemic use may cause significant toxicity.
Polymyxin B
- Applied topically for ear, eye, and skin infections, often in combination with other agents.
- Not recommended for systemic infections due to the risk of toxicity.

Systemic Mycoses

Challenging treatment; often resistant to therapy.
Long-term treatment may involve potentially toxic drugs.

Major Groups of Antifungal Agents

Systemic Mycoses Infections
- Opportunistic: Candidiasis, aspergillosis, cryptococcosis, mucormycosis occur in immunocompromised hosts.
- Non-opportunistic: Sporotrichosis, blastomycosis, histoplasmosis, coccidioidomycosis can affect any host.
Superficial Mycoses Infections
- Includes candidiasis and dermatophyte infections; some drugs treat both types.

Amphotericin B

Recognized as a broad-spectrum antifungal, also active against certain protozoa.
Known for high toxicity; causes infusion reactions and renal damage in all patients.
Exclusively administered intravenously; oral administration is not possible.
Considered the drug of choice for most systemic mycoses, with prior systemic fungal infections often being fatal.

Azoles (“-azole”)

Broad-spectrum antifungal agents include ketoconazole, fluconazole, and itraconazole.
Serve as an alternative to amphotericin B for most systemic mycoses with lower toxicity.
Can be administered orally but may inhibit P450 enzymes, raising levels of various other medications.

Antiviral Therapy

Treatment for viral infections remains limited due to the challenge of suppressing viral replication without harming host cells.
Antivirals are designed to target biochemical processes unique to viral reproduction.

Acyclovir (Zovirax)

Active specifically against herpesvirus family members.
First-choice treatment for infections such as herpes simplex genitalis, mucocutaneous herpes simplex, varicella-zoster, and cytomegalovirus (CMV).

Valacyclovir (Valtrex)

Acts as a prodrug form of acyclovir.
Prescribed for herpes zoster, herpes simplex genitalis, and herpes labialis.
In immunocompromised patients, it may cause thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS).

Description

Explore the pharmacological functions and side effects of Metronidazole and other antibacterial drugs like Rifampin and Rifaximin. This quiz covers their uses against specific infections, including their impact on various pathogens and important cautions for use. Test your understanding of their mechanisms and patient management considerations.