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Pentoxyphyllin pharmacology

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pentoxifylline FDA label pharmacology mechanism warnings

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https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=73a…

Pentoxifylline pharmacology

Pentoxifylline is a methylxanthine derivative and hemorheologic agent. It improves blood flow properties rather than acting as a direct vasodilator.

Mechanism of action

  • Reduces whole-blood viscosity.
  • Increases erythrocyte flexibility (deformability), helping red cells pass through narrowed microcirculation.
  • Reduces platelet aggregation and may reduce leukocyte adhesion/activation.
  • Net effect: improved microvascular blood flow and tissue oxygen delivery.
  • It has weak, nonselective phosphodiesterase-inhibitory effects, but its clinical benefit is principally attributed to these hemorheologic actions.
The precise sequence linking these effects to symptomatic improvement is not fully established. The DailyMed prescribing information describes dose-related reductions in blood viscosity and improved erythrocyte flexibility.

Main clinical use

  • Intermittent claudication due to chronic peripheral arterial disease: used to improve walking symptoms, though benefit is generally modest.
  • It does not replace smoking cessation, supervised exercise, antiplatelet/statin therapy, cardiovascular risk-factor control, or revascularization when indicated.
Current Surgical Therapy describes its symptom benefit as modest and notes reduction in blood viscosity and platelet aggregation as its key effects, p. 1143.

Pharmacokinetics

  • Given orally, commonly as extended-release 400 mg tablets.
  • Almost completely absorbed, but undergoes substantial first-pass metabolism.
  • Major active metabolites reach plasma concentrations greater than the parent drug.
  • Parent-drug half-life: roughly 0.4 to 0.8 hours; metabolite half-lives are about 1 to 1.6 hours.
  • Excretion is mainly renal as metabolites. Dose reduction is needed in significant renal impairment.

Usual dose

  • 400 mg orally three times daily with meals is the typical extended-release regimen.
  • If adverse effects occur, the dose may be reduced to 400 mg twice daily.
  • Swallow extended-release tablets whole. Do not crush or chew.

Adverse effects

Common:
  • Nausea, dyspepsia, vomiting
  • Headache, dizziness, drowsiness
  • Flushing
  • Anorexia
Important but less common:
  • Hypotension, tachycardia/arrhythmias
  • Bleeding, particularly in people receiving antiplatelets, anticoagulants, or NSAIDs
  • Rare hypersensitivity reactions

Contraindications and precautions

Avoid/contraindicated in:
  • Recent cerebral hemorrhage
  • Recent retinal hemorrhage
  • Previous intolerance or hypersensitivity to pentoxifylline or other methylxanthines
Use cautiously in:
  • Patients at increased bleeding risk, including recent surgery or peptic ulcer disease
  • Severe renal impairment
  • Hepatic impairment
  • Patients prone to hypotension or taking antihypertensives

Important interactions

  • Warfarin, heparin, antiplatelet drugs, NSAIDs: may increase bleeding risk. Monitor for bleeding; warfarin-treated patients need closer PT/INR monitoring.
  • Theophylline: pentoxifylline can increase theophylline concentrations, so monitor levels and toxicity.
  • Antihypertensives: additive blood-pressure lowering may occur.
  • Insulin and oral hypoglycemics: may enhance glucose-lowering effect in some patients, so glucose monitoring may be needed.

One-line exam summary

Pentoxifylline is an oral methylxanthine-derived hemorheologic drug used for intermittent claudication; it decreases blood viscosity, increases red-cell deformability, and reduces platelet aggregation, thereby improving microcirculatory flow.
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