Griseofulvin and Squalene Epoxidase Inhibitor (Terbinafine) – Antifungals

00:00 Griseofulvin is a medication that does not neatly fall into one of the usual antifungal drug classes.

00:07 Now it is not active topically.

00:09 It actually an orally ingested agent for skin infections.

00:14 So that's sometimes kind of confusing to a lot of medical students.

00:18 It's a skin drug but it's not used topically.

00:21 It's distributed to the stratum corneum where it binds to various proteins.

00:27 It should not be used in patients with porphyria because you can actually precipitate a porphyria crisis with this agent.

00:36 In terms of how it works, it actually inhibits microtubule formation in the dermatophytes.

00:41 It's a fungistatic so it's absorbed into fungal cells through an active transporter.

00:47 The toxicity of this agent includes, headache and GI distress, fever, rash and flushing from the histamine release that you sometimes get.

00:55 Now the other thing that's really important with this agent is that it will interfere with warfarin levels.

01:00 So be careful of your warfarin dosing in your INR's when you start this medication.

01:08 Terbinafine is available both in oral and in topical forms.

01:13 Like griseofulvin it is distributed to the stratum corneum where it binds to various proteins.

01:19 It's actually much more effective then griseofulvin.

01:24 And we see it all the time used in fungal infections.

01:29 In terms of how it works, it inhibits squalene epoxidase.

01:35 It accumulates, there's an accumulation of squalene and this interferes with ergosterol synthesis.

01:43 And this is actually a fungicidal activity.

01:46 Toxicity once again same as the other ones.

01:49 Headache, GI distress, fever, rash and flushing from histamine release.

01:53 And once again this drug also will interfere with warfarin dosing and levels.