Pentoxifylline
Pentoxifylline is a synthetic **methylxanthine derivative** (structurally related to theophylline and caffeine) with unique hemorrheologic and immunomodulatory properties. * **Dogs**: Primarily used to treat immune-mediated dermatologic conditions with underlying microvascular compromise, such as **familial canine dermatomyositis**, ear margin seborrhea/necrosis, and cutaneous vasculitis (e.g., Alabama rot). It is also used adjunctively for atopic dermatitis and is being investigated for dilated cardiomyopathy (DCM). * **Horses**: Used as adjunctive therapy for cutaneous vasculitis, endotoxemia, navicular disease, and placentitis. * **Cats**: Occasionally used alongside prednisolone to decrease vasculitis associated with Feline Infectious Peritonitis (FIP). > **Clinical Pearl**: Because its effects on tissue remodeling and inflammation take time, clinical benefits in dermatologic conditions may not be seen for 4 to 8 weeks.
Mechanism: The exact mechanisms are multifaceted, combining rheological improvement with anti-inflammatory effects: * **Phosphodiesterase (PDE) Inhibition**: Inhibits erythrocyte PDE โ increases intracellular cAMP โ increases erythrocyte flexibility and deformability, allowing red blood cells to navigate compromised microvasculature. * **Blood Viscosity Reduction**: Reduces plasma fibrinogen and increases fibrinolytic activity. * **Immunomodulation**: PDE inhibition in leukocytes decreases the production of inflammatory cytokines, notably **TNF-ฮฑ**, reducing the negative effects of endotoxemia. * **Enzyme Inhibition**: In horses, it acts as a potent inhibitor of **matrix metalloproteinase-9 (MMP-9)** and a modest inhibitor of **MMP-2**, which may aid in preventing tissue degradation.
Dosing by species
- Vasculitis (off-label) ยท 15 mg/kg ยท PO ยท q12h ยท As directed ยท Rarely used in cats.
- Cutaneous vasculitis / General ยท 10 mg/kg q12h PO ยท PO ยท q12h ยท 30 days ยท OK to crush the sustained-release tablets and mix with molasses. If efficacy wanes with time, consider increasing the dose to 15 mg/kg PO twice daily or 10 mg/kg PO three times a day.
- Adjunctive treatment to prevent GI thrombosis ยท 7.5 mg/kg IV q12 hours ยท IV ยท q12h ยท Can be easily filtered in a 0.5 micron filter for IV use
- To reduce cytokine effects in endotoxemia ยท 7.5 mg/kg PO q12h ยท PO ยท q12h ยท Efficacy may be improved if used with flunixin
- To reduce cytokine effects in endotoxemia ยท 8 mg/kg PO q8h ยท PO ยท q8h
- Adjunctive treatment (experimental) of sepsis in foals ยท 7.5 mg/kg IV bolus, followed by a CRI of 1.5 mg/kg/hour ยท IV ยท Bolus then CRI ยท Has been shown to increase regional blood flow and suppress coagulation.
- Adjunctive treatment of equine pastern dermatitis ยท 4-8 mg/kg PO q12h ยท PO ยท q12h ยท Add if clinical signs do not resolve after 14 days of topical and other immunomodulating therapy
- To increase oxygenation of placenta in placentitis ยท 7.5 mg/kg PO q12h ยท PO ยท q12h
- To increase the circulation to the podotrochlea ยท 4.5-7 mg/kg PO three times daily ยท PO ยท TID
Routes of administration
Contraindications
- Intolerance or hypersensitivity to pentoxifylline or other xanthines (e.g., theophylline, caffeine, theobromine)
- Cerebral hemorrhage
- Retinal hemorrhage
- Hypersensitivity to methylxanthines (e.g., theophylline, caffeine)
- Cerebral or retinal hemorrhage
- Severe hepatic or renal impairment (use with caution)
Adverse effects
- Vomiting
- Inappetence
- Loose stools
- Excitement
- Nervousness
- Dizziness (humans)
- Headache (humans)
- Erythema multiforme (rare in dogs)
- Transient leukocytosis (horses IV)
- Muscle fasciculations (horses IV)
- Sweating on shoulders/flanks (horses IV)
- Mild increases in heart rate (horses IV)
- Anorexia
- Diarrhea
- Restlessness
- Tachycardia
- Tremors
Drug interactions
- Antihypertensive drugs ยท May increase hypotensive effect when used concurrently
- NSAIDs ยท Controversial in horses; may negate beneficial effects for endotoxemia, though some studies show superior efficacy when used with flunixin
- Platelet-aggregation inhibitors (e.g., aspirin, clopidogrel) ยท Increased risk for bleeding
- Theophylline ยท Serum levels of theophylline may be increased when used concurrently ยท major
- Warfarin ยท Increased risk of bleeding; use together with enhanced monitoring and caution ยท moderate
- Ciprofloxacin ยท May increase pentoxifylline levels ยท moderate
- Antihypertensives ยท Potential for additive hypotensive effects ยท minor
Monitoring
- Clinical efficacy (resolution of dermatologic or vascular signs)
- Adverse effects (GI upset, CNS signs)
- Clinical response (resolution of skin lesions/improved blood flow)
- Gastrointestinal tolerance
- Signs of bleeding
Overdose
Signs of overdose in humans include **flushing, seizures, hypotension, unconsciousness, agitation, fever, somnolence, GI distress, and ECG changes**. One patient who ingested 80 mg/kg recovered completely. Overdoses should be treated using standard methods of appropriate gut emptying (emesis/lavage) and supportive therapies.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.