Antiviral and antifungal meds Flashcards
What is an anti-viral agent?
A medication that helps the body fight off viruses
Only Interferon licensed in veterinary species
What is the difference between an anti-viral and a viricide?
Anti-virals work inside host to inhibit viral replication
Viricides destroy viruses outside host (e.g. Virkon)
Describe the ways that anti-viral drugs work
Stop replication of the virus in the cell
Block the ability of a virus to attach/enter host cells
Immune response enhancement
Why do antiviral drugs have a narrow therapeutic margin?
Since viruses use host cell machinery for replication, antiviral drugs can also affect normal host pathways
This increases risk of toxicity & limits treatment options compared to antibacterial or antifungal drugs
What is a virustatic drug, and why is it not always effective?
Inhibits 1 step in viral replication but doesn’t kill virus
Only temporarily halts replication, meaning virus may resume growth if drug is stopped
What are the two main antiviral treatments for feline herpesvirus (FHV-1)?
Trifluridine – topical nucleoside analogue used for ocular herpes infection
Famciclovir – Oral (systemic) nucleoside analogue that reduces respiratory & ocular signs
Why are antivirals rarely used for feline calicivirus (FCV)?
Most antivirals are ineffective or toxic to cats, so treatment focuses on supportive care
What is Feline interferon w & what is it used for
Immunomodulator with possible antiviral activity
Used in:
- FCV
- Feline Chronic Gingivostomatitis (FCGS)
- FeLV
- FIV
- Canine parvovirus
What antiviral is sometimes used for FIP (cat coronavirus)
Remdesivir (protease inhibitor)
What antiviral is used for Pacheco’s disease (a herpesvirus) in birds, and how does it work?
Aciclovir (nucleoside analogue)
It incorporates into viral DNA, causing chain termination & stopping viral replication
Resistance is increasing, making treatment less effective
What are the different types of anti-fungal drugs?
azoles
allylamines
polyenes
pyrimidine analogues
Give examples of azoles (anti-fungals)
itraconazole, ketoconazole
How do azoles (antifungals) work?
Inhibit cytochrome P450-dependent synthesis of ergosterol in fungal cells.
Give examples of allylamines (anti-fungals)
terbinafine
How do allylamines (anti-fungals) work?
Inhibit squalene epoxidase (key enzyme in ergosterol synthesis) causing ergosterol depletion & toxic buildup, leading to fungal cell death
How do polyenes (anti-fungals) work?
Bind to ergosterol in fungal cell membranes, creating pores that cause leakage of intracellular contents, leading to fungal cell death
Give an example of a pyrimidine analogue (anti-fungal)
5-fluorocytosine
How do pyrimidine analogues (antifungals) work?
5-Fluorocytosine is converted by fungal cells into 5-fluorouracil, which inhibits DNA & RNA synthesis, stopping fungal replication
What are cellular toxins, and how do they work against fungi?
Cellular toxins are non-specific antimicrobials that have antifungal activity by disrupting fungal cells through chemical toxicity or membrane damage
Give examples of cellular toxins with antifungal properties
Silver sulfadiazine - Releases silver in concentrations that are toxic to bacteria and yeasts
Chlorhexidine (Hibiscrub) – antiseptic - Binds to the skin and forms a protective layer
Virkon - disinfectant - Per-oxygen compound that oxidizes sulphur bonds in proteins and enzymes disrupting the function of thecell membrane.
What anti-fungal drugs can be used to treat otitis externa (malassezia) in cats and dogs?
Nystatin
Miconazole
Clotrimazole - off licence in cats
Terbinafine - do not use in cats
Posaconazole - off licence in cats
What anti-fungal drugs can be used to treat malassezia skin infections in cats and dogs?
Miconazole - shampoo
Climbazole - wipes
Itraconazole - off licence in dogs; oral; systemic treatment
Ketoconazole – do NOT use in cats; oral, shampoo or skin spray
Chlorhexidine - shampoo/foam/spray/otic solution/wipes
What anti-fungal drugs can be used to treat dermatophytosis (ringworm) in cats and dogs?
Itraconazole - off licence in dogs
Ketoconazole - do NOT use in cats
Enilconazole - off licence in cats
Miconazole - shampoo; adjunctive treatment
Chlorhexidine - shampoo/foam/spray/otic solution/wipes; synergistic with miconazole, ineffective alone
Clotrimazole - off licence; cream; adjunctive treatment
