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.