Understanding Medications: What Are Examples of Antimicrobials?

October 14, 2025 •

4 min read

Since the discovery of penicillin in 1928, antimicrobial agents have revolutionized medicine by treating infectious diseases. These powerful substances inhibit or destroy the growth of microorganisms, and understanding what are examples of antimicrobials is key to appreciating their diverse functions in medicine.

Quick Summary

Antimicrobials are a broad class of agents that inhibit or kill microorganisms such as bacteria, fungi, viruses, and parasites. This group encompasses many types, including antibiotics, antivirals, and antifungals, which use different mechanisms to combat infection.

Key Points

Broad Category: Antimicrobials are a general class that includes antibiotics, antivirals, antifungals, and antiparasitics, each targeting different microorganisms.
Antibiotics Target Bacteria: Antibiotics like amoxicillin and ciprofloxacin combat bacterial infections by inhibiting cell wall or protein synthesis.
Antifungals Fight Fungi: Antifungal agents such as fluconazole and amphotericin B treat infections caused by fungi by damaging their cell membranes or cell walls.
Antivirals Inhibit Viruses: Antivirals like acyclovir and oseltamivir are used for specific viral infections and work by disrupting viral replication.
Topical vs. Systemic: Antiseptics are applied to living tissue, while disinfectants are used on inanimate objects to control microbial growth.
Resistance is a Challenge: Misuse and overuse of antimicrobials have led to widespread drug resistance, necessitating careful prescribing and stewardship programs.

Antimicrobial agents are a cornerstone of modern medicine, extending far beyond the common antibiotics used to treat bacterial infections. This diverse group of substances includes drugs that combat bacteria, fungi, viruses, and parasites. Their development has significantly reduced mortality from infectious diseases, though the threat of antimicrobial resistance remains a major public health challenge.

The Broad Spectrum of Antimicrobial Agents

Antibacterials (Antibiotics)

Antibiotics are arguably the most well-known antimicrobials, specifically targeting bacteria. They can be classified by their structure and mechanism of action. Examples of different classes include:

Penicillins: Examples are amoxicillin and penicillin V, which work by inhibiting bacterial cell wall synthesis.
Cephalosporins: Examples like cephalexin and cefazolin also interfere with bacterial cell wall construction.
Macrolides: Erythromycin and azithromycin are examples that inhibit bacterial protein synthesis [1.4.1, 4.3].
Fluoroquinolones: Ciprofloxacin and levofloxacin target bacterial DNA synthesis.
Tetracyclines: Doxycycline and minocycline block protein synthesis by binding to ribosomes.
Aminoglycosides: Gentamicin and tobramycin also inhibit protein synthesis and are often used for serious infections.
Glycopeptides: Vancomycin is an example used for severe bacterial infections, including MRSA, by inhibiting cell wall synthesis.

Antifungals

Antifungals are used to treat infections caused by fungi, such as yeasts and molds. Because fungi are eukaryotes like human cells, developing effective and safe antifungals is challenging.

Azoles: Fluconazole, itraconazole, and ketoconazole are common azoles that prevent fungi from growing by blocking ergosterol synthesis, a key component of their cell membranes.
Polyenes: Amphotericin B and nystatin disrupt the fungal cell membrane directly.
Echinocandins: This newer class, including caspofungin and micafungin, attacks the fungal cell wall.

Antivirals

Antivirals target specific viral infections by inhibiting different stages of the viral life cycle.

Herpesvirus agents: Acyclovir and valacyclovir are used to treat infections like herpes and chickenpox by interfering with viral replication.
Influenza treatments: Oseltamivir (Tamiflu) and zanamivir (Relenza) inhibit the release of new virus particles from infected cells.
HIV medications: Retroviral drugs like abacavir and ritonavir target specific steps in the HIV replication process.
COVID-19 treatments: Remdesivir is an example of an antiviral used to treat specific cases of COVID-19.

Antiparasitics

These agents are used to treat infectious diseases caused by parasites, including protozoa and helminths (worms).

Antiprotozoal agents: Metronidazole and tinidazole are used for protozoal infections like giardiasis and trichomoniasis.
Antimalarial drugs: Chloroquine and artemether/lumefantrine are used to treat malaria, caused by the Plasmodium parasite.
Anthelmintic agents: Ivermectin and albendazole are effective against parasitic worms.

Antiseptics and Disinfectants

These topical antimicrobials differ from systemic medications. Antiseptics are applied to living tissue, while disinfectants are used on non-living surfaces.

Antiseptics: Chlorhexidine is a common antiseptic used to clean skin before surgery or other procedures. Alcohol-based hand sanitizers are another familiar example.
Disinfectants: Bleach and quaternary ammonium salts are examples of disinfectants used on surfaces in homes and hospitals.

Antimicrobial Comparison Table


Type of Antimicrobial	Target Microorganism(s)	Example Drug	Key Mechanism of Action
Antibacterial	Bacteria	Ciprofloxacin	Inhibits bacterial DNA synthesis
Antibacterial	Bacteria	Amoxicillin	Inhibits bacterial cell wall synthesis
Antifungal	Fungi (yeasts, molds)	Fluconazole	Disrupts fungal cell membrane by inhibiting ergosterol synthesis
Antiviral	Viruses	Acyclovir	Interferes with viral replication
Antiparasitic	Protozoa	Metronidazole	Damages parasite DNA
Antiparasitic	Helminths (worms)	Ivermectin	Paralyses and kills parasitic worms
Antiseptic	Microorganisms on skin	Chlorhexidine	Damages cell membranes and inactivates enzymes

The Threat of Antimicrobial Resistance

The misuse and overuse of antimicrobial agents, particularly antibiotics, are the primary drivers of antimicrobial resistance. Bacteria, fungi, and other microbes can evolve and develop mechanisms to withstand these drugs, making infections harder to treat. This is a serious threat to global public health, and responsible use is critical to slow its progression. Efforts like antimicrobial stewardship programs are designed to promote appropriate use in healthcare settings.

How Antimicrobials Are Chosen and Administered

Selecting the right antimicrobial depends on several factors, including the type of pathogen causing the infection, the infection's location, and patient-specific factors such as age, allergies, and kidney or liver function. Diagnostic tests, such as culturing, help identify the specific pathogen and its susceptibility to different drugs. The treatment approach may start with a broad-spectrum agent but should be narrowed to a more specific one once test results are available to reduce the risk of resistance. Antimicrobials are available in various forms, including oral tablets, capsules, liquids, topical creams, eye drops, and injections. For more information on the principles of antimicrobial therapy, refer to the NCBI Medical Microbiology resource.

Conclusion

Antimicrobial agents are a vast and vital category of medications used to combat infections caused by a wide range of microorganisms. From common antibiotics like amoxicillin to specialized antivirals like acyclovir, these drugs have distinct mechanisms of action tailored to their targets. However, the rise of antimicrobial resistance underscores the importance of careful prescription and patient education to preserve the effectiveness of these life-saving drugs.

Frequently Asked Questions

An antimicrobial is a broad term for any agent that kills or inhibits microorganisms, including bacteria, viruses, fungi, and parasites. An antibiotic is a specific type of antimicrobial that is only effective against bacteria.

Antibacterials (antibiotics) are not effective against viruses, including the common cold or flu. Antiviral medications are specifically required to treat viral infections. For many mild viral infections, treatment is supportive, as no specific antiviral is needed.

Antifungal medications work by exploiting the differences between fungal and human cells. Many target the fungal cell membrane by inhibiting the production of ergosterol or by directly disrupting the membrane's integrity, killing the fungal cells.

Antimicrobial resistance occurs when microorganisms evolve to withstand the effects of drugs. This makes previously treatable infections difficult or impossible to cure, leading to higher healthcare costs, prolonged hospital stays, and increased mortality.

An antiseptic is an antimicrobial agent applied to living tissue, like skin, to prevent infection. A disinfectant is a chemical agent used to eliminate microorganisms on non-living surfaces, such as countertops or medical instruments.

Healthcare providers select antimicrobials based on the type of infection, the specific pathogen identified (often through laboratory cultures), the site of infection, and patient-specific factors such as allergies or kidney function. Using a narrow-spectrum agent when possible helps reduce resistance.

Side effects vary greatly depending on the specific agent. Some common effects include gastrointestinal upset, skin rashes, and allergic reactions. Prolonged use can sometimes disrupt the body's natural microflora.