pentoxifylline
Trental

Available forms
Available by prescription only
Tablets (extended-release): 400 mg

Indications and dosages
 Intermittent claudication from chronic occlusive vascular disease. Adults: 400 mg P.O. t.i.d. with meals.

Pharmacodynamics
Hemorrheologic action: Improves capillary blood flow by increasing erythrocyte flexibility and reducing blood viscosity.

Pharmacokinetics
Absorption: Absorbed almost completely from GI tract but undergoes first-pass hepatic metabolism. Absorption slowed by food. Clinical effect requires 2 to 4 weeks of continued therapy.
Distribution: No information available; bound to erythrocyte membrane.
Metabolism: Metabolized extensively by erythrocytes and liver.
Excretion: Metabolites excreted principally in urine; less than 4% of drug excreted in feces. Half-life of unchanged drug is about 1/2 to 3/4 hour; half-life of metabolites is about 1 to 1 1/2 hours.

Contraindications and precautions
Contraindicated in patients who are intolerant to pentoxifylline or methylxanthines (such as caffeine, theophylline, and theobromine) and in patients with recent cerebral or retinal hemorrhage. Use cautiously in elderly patients.

Interactions
Drug-drug. Antihypertensives: Increases hypotensive response. Monitor blood pressure.
Drugs that inhibit platelet aggregation, oral anticoagulants (such as warfarin): Causes bleeding abnormalities. Monitor PT and INR.
Theophylline: Increases theophylline levels. Monitor patient closely.

Adverse reactions
CNS: headache, dizziness.
CV: angina pectoris, chest pain.
GI: dyspepsia, nausea, vomiting, flatus, bloating.

Effects on lab test results
None reported.

Overdose and treatment
Signs and symptoms of overdose include flushing, hypotension, seizures, somnolence, loss of consciousness, fever, and agitation.
 There’s no known antidote. Empty stomach by gastric lavage and use activated charcoal; treat symptoms and support respiration and blood pressure.

Special considerations
• If GI and CNS adverse effects occur, decrease dosage to twice daily. If adverse effects persist, stop drug.
• Drug is useful in patients who aren’t good candidates for surgery.
• Don’t crush or break extended-release tablets; make sure patient swallows them whole.
• Monitor blood pressure regularly, especially in patients taking antihypertensives.
• Monitor INR, especially in patients taking anticoagulants such as warfarin.
Breast-feeding patients
• Drug appears in breast milk. An alternative to breast-feeding is recommended during therapy.
Pediatric patients
• Safety and efficacy haven’t been established for patients younger than age 18.
Geriatric patients
• Elderly patients may have increased bioavailability and decreased excretion of drug and, thus, are at higher risk for toxicity; adverse reactions may be more common in elderly patients.

Patient education
• Explain need for continuing therapy for at least 8 weeks; warn patient not to stop drug during this period without approval.
• Advise patient to take drug with meals to minimize GI distress.
• Tell patient to report GI or CNS adverse reactions; dosage reduction may be needed.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use