The quality of evidence is downgraded by study limitations (unclear allocation concealment and blinding), by inconsistency (unexplained variability in results), and by indirectness (differences between the outcomes of interest and those reported: lack of quality of life outcomes).
A Cochrane review [Abstract] 1 included 18 studies with a total of 2 773 subjects. The aim of the review was to determine the efficacy of prostanoids (prostaglandin E1 (PGE1), prostacyclin (PGI2) and analogues such as iloprost, beraprost, taprostene, ciprostene) in improving walking distance and other objective and subjective outcomes in patients with intermittent claudication Fontaine stage II. It was not possible to meaningfully pool results by meta-analysis.
Four studies compared prostaglandin PGE1 with placebo; individual studies showed significant increases in walking distances with administration of PGE1 and in several studies the walking capacity remained increased after termination of treatment. Compared with pentoxifylline, PGE1 was associated with a higher final pain-free walking distance (PFWD) and maximum walking distance (MWD) but these results were based on final walking distances rather than changes in walking distance from baseline. When PGE1 was compared with other treatments including laevadosin, naftidrofuryl and L-arginine, improvements in walking distances over time were observed for both PGE1 and the alternative treatment, but it was not possible from the data available to analyse statistically whether or not one treatment was more effective than the other.
Six studies compared various preparations of PGI2 with placebo. In one study using three different dosages of iloprost, PFWD and MWD appeared to increase in a dose-dependent manner; iloprost was associated with headache, pain, nausea and diarrhoea, leading to a higher rate of treatment withdrawal. Of three studies using beraprost sodium, one showed an improvement in PFWD and MWD compared with placebo while two showed no significant benefit. Beraprost sodium was associated with an increased incidence of drug-related adverse events.
Comprehensive, high quality data on outcomes such as quality of life, ankle brachial index, venous occlusion plethysmography and haemorrheological parameters were lacking.
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