Article Text
Abstract
Many drugs are recommended for the treatment of peripheral vascular disease but evidence for their usefulness is conflicting, mainly because the drug responses are difficult to assess. For instance a symptom such as intermittent claudication may fluctuate spontaneously1 and is also particularly susceptible to a placebo effect.2 Objective criteria may also mislead, for an increase in the blood flow in the ischaemic limb during exercise does not necessarily correlate with symptomatic improvement,3 and in healthy limbs the response to a drug may be quite different from that in a diseased one. In the diseased limb, for instance, a vasodilator drug may not increase the blood flow above that already produced by the local accumulation of metabolites,4 and furthermore any drug that causes widespread dilatation in normal vessels may reduce the perfusion pressure and thus the flow to the ischaemic limb,5 or may shunt blood away from ischaemic zones towards normal areas.