Pentoxifylline (PTX)

What is this medication for?

• Immune-mediated dermatoses: dermatomyositis, Sheltie/Collie ulcerative dermatosis, lupoid onychodystrophy, vasculitis, contact/ear-margin dermatoses — anywhere microcirculation + neutrophil modulation helps; NOT first-line for atopic dermatitis (modest benefit, Olivry 2010)
• DCM adjunct

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.

• Cheap steroid-sparing adjunct, never first-line for atopy — pair with the expectations conversation (weeks to effect).

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 (vomiting, inappetence, loose stools) — most common (Dose-related)
• CNS excitement/nervousness (Occasional)

Worth a phone call to your veterinarian

• Erythema multiforme (Rare)

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

• Human overdose: flushing, seizures, low blood pressure, somnolence, ECG changes (High-dose picture)

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

• has or has had: Retinal or cerebral bleeding; xanthine hypersensitivity (theophylline cross)
• has or has had: Severe hepatic/renal impairment; bleeding risk (trauma, coagulopathy)

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Warfarin/anticoagulants
  • Antihypertensives
  • Theophylline-class
  • Cimetidine (human)

Storage and handling

SR tablets — often crushed/dosed whole in dogs; food co-administration for stomach/intestinal tolerance.

Good to know

• The "blood-thinner that isn't an anticoagulant": improves flow through damaged microvasculature (RBC deformability) + damps neutrophil/TNF inflammation — the logic behind ulcerative dermatosis and vasculitis use in rough-coated breeds.
• Cheap steroid-sparing adjunct, never first-line for atopy — pair with the expectations conversation (weeks to effect).
• Warfarin co-use bleeding flag is the dispensing-relevant interaction.