Pentoxifylline for intermittent claudication

Abstract

Background: Intermittent claudication (IC) is a symptom of peripheral arterial disease (PAD) and is associated with high morbidity and mortality. Pentoxifylline, one of many drugs used to treat IC, acts by decreasing blood viscosity, improving erythrocyte flexibility, and promoting microcirculatory flow and tissue oxygen concentration. Many studies have evaluated the efficacy of pentoxifylline in treating people with PAD, but results of these studies are variable. This is the second update of a review first published in 2012. Objectives: To determine the efficacy of pentoxifylline in improving the walking capacity (i.e. pain-free walking distance and total (absolute, maximum) walking distance) of people with stable intermittent claudication, Fontaine stage II. Search methods: For this update, the Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases, and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 28 January 2020. There were no language restrictions. Selection criteria: We included all double-blind, randomised controlled trials (RCTs) comparing pentoxifylline versus placebo or any other pharmacological intervention in people with IC Fontaine stage II. Data collection and analysis: Two review authors independently selected studies for inclusion, assessed the included studies, matched data and resolved disagreements by discussion. Review authors assessed the methodological quality of studies using the Cochrane 'Risk of bias' tool and collected results related to the outcomes of interest, pain-free walking distance (PFWD), total walking distance (TWD), ankle-brachial pressure index (ABI), quality of life (QoL) and side effects. Comparison of studies was based on duration and dose of pentoxifylline. We used GRADE criteria to assess the certainty of the evidence. Main results: We identified no new eligible studies for this update. This review includes 24 studies with 3377 participants. Seventeen studies compared pentoxifylline versus placebo. The seven remaining studies compared pentoxifylline with flunarizine (one study), aspirin (one study), Gingko biloba extract (one study), nylidrin hydrochloride (one study), prostaglandin E1 (two studies), and buflomedil and nifedipine (one study). Risk of bias for the individual studies was generally unclear because there was a lack of methodological reporting for many of the included studies, especially regarding randomisation and allocation methods. Most included studies did not provide adequate information to allow selective reporting to be judged and did not report blinding of assessors. Heterogeneity between included studies was considerable with regards to multiple variables, including duration of treatment, dose of pentoxifylline, baseline walking distance and participant characteristics; therefore, pooled analysis for comparisons which included more than one study, was not possible. Pentoxifylline compared to placebo. Of 17 studies comparing pentoxifylline with placebo, 11 reported PFWD and 14 reported TWD; the difference in percentage improvement in PFWD for pentoxifylline over placebo ranged from –33.8% to 73.9% and in TWD ranged from 1.2% to 155.9%. It was not possible to pool the data of the studies because data were insufficient and findings from individual trials were unclear. Most included studies suggested a possible improvement in PFWD and TWD for pentoxifylline over placebo (both low-certainty evidence). The five studies which evaluated pre-exercise ABI comparing pentoxifylline and placebo found no evidence of a difference (moderate-certainty evidence). Two of the three studies that evaluated QoL between people who received pentoxifylline and placebo were larger studies that used validated QoL tools and generally found no evidence of a difference between groups. One small, short-term study, which did not specify which QoL tool was used, reported improved QoL in the pentoxifylline group (moderate-certainty evidence). Pentoxifylline generally was well tolerated; the most commonly reported side effects consisted of gastrointestinal symptoms such as nausea (low-certainty evidence). Certainty of the evidence from this review was low or moderate, with downgrading due to risk of bias concerns, inconsistencies between studies and the inability to evaluate imprecision because meta-analysis could not be undertaken. The seven remaining studies compared pentoxifylline with either flunarizine, aspirin, Gingko biloba extract, nylidrin hydrochloride, prostaglandin E1, or buflomedil and nifedipine; data were too limited to allow any meaningful conclusions to be made. Authors' conclusions: There is a lack of high-certainty evidence for the effects of pentoxifylline compared to placebo, or other treatments, for IC. There is low-certainty evidence that pentoxifylline may improve PFWD and TWD compared to placebo, but no evidence of a benefit to ABI or QoL (moderate-certainty evidence). Pentoxifylline was reported to be generally well tolerated (low-certainty evidence). Given the large degree of heterogeneity between the studies, the role of pentoxifylline for people with IC Fontaine class II remains uncertain.