Griseofulvin

What is this medication for?

• Dermatophytosis (Microsporum, Trichophyton, Epidermophyton) of skin/hair/claws
• Malassezia, other fungi, bacteria

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Fungistatic, not fungicidal — it only protects newly grown keratin: treatment length = a full hair-coat/claw growth cycle (weeks to months), and cure is confirmed by culture, not just look.
• Griseofulvin vs itraconazole in cats: itraconazole's better safety profile (no teratogenicity at clinical doses, no marrow risk) has made it first-line; griseofulvin persists where itraconazole isn't available/affordable — but NEVER in pregnant or FIV-positive cats.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• stomach/intestinal (loss of appetite, vomiting, diarrhea) (Most common)

Worth a phone call to your veterinarian

• Bone marrow suppression (low infection-fighting cell counts, low red blood cell counts, low platelet counts; panleukopenia-like) (Kittens/cats — glucuronidation-slow)
• Hepatotoxicity, wobbliness/unsteadiness, depression, photosensitivity/dermatitis, TEN (Uncommon)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Pregnancy (teratogen); hepatocellular failure; hypersensitivity
• has or has had: Kittens (monitor carefully); test cats for FIV before starting (low infection-fighting cell counts risk); cats generally = dose-careful species

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Phenobarbital (CYP inducers)
  • Warfarin
  • Cyclosporine
  • Alcohol (human)

Storage and handling

Room temperature. Availability declining; human products used.

Good to know

• Fungistatic, not fungicidal — it only protects newly grown keratin: treatment length = a full hair-coat/claw growth cycle (weeks to months), and cure is confirmed by culture, not just look.
• Fat co-administration is absorption pharmacology in action (microsize) — corn oil trick.
• Griseofulvin vs itraconazole in cats: itraconazole's better safety profile (no teratogenicity at clinical doses, no marrow risk) has made it first-line; griseofulvin persists where itraconazole isn't available/affordable — but NEVER in pregnant or FIV-positive cats.
• Microsize vs ultramicrosize dosing is not interchangeable (~1.5× potency difference).