A double-blind comparison of topical capsaicin and oral amitriptyline in painful diabetic neuropathy.

An 8-week double-blind, multicenter, parallel study compared the safety and efficacy of topical capsaicin and oral amitriptyline in patients with painful diabetic neuropathy involving the feet. Two hundred thirty-five patients were randomized to treatment with either capsaicin cream or amitriptyline capsules. Capsaicin-treated patients received inactive capsules, and amitriptyline-treated patients applied vehicle cream. A visual analogue scale of pain intensity and measurements of interference by pain with functional activities were recorded at onset and at 2-week intervals. A visual analogue scale of pain relief and physicians' global evaluation assessed changes in pain status from baseline. Topical capsaicin and oral amitriptyline produced equal and statistically significant improvements in pain over the course of the study. By the end of week 8, 76% of patients in each group experienced less pain, with a mean reduction in intensity of more than 40%. By the end of the study, the interference with daily activities by pain had diminished significantly (P = .001) in both groups, including improvements in sleeping and walking. No systemic side effects were observed in patients treated with topical capsaicin. Most patients receiving amitriptyline experienced at least one systemic side effect, ranging from somnolence (46%) to neuromuscular (23%) and cardiovascular (9%) adverse effects. Topically applied capsaicin is an equally effective but considerably safer alternative to amitriptyline for relief of the pain of diabetic neuropathy.

Specific high-affinity binding of high density lipoproteins to cultured human skin fibroblasts and arterial smooth muscle cells.

Binding of human high density lipoproteins (HDL, d = 1.063-1.21) to cultured human fibroblasts and human arterial smooth muscle cells was studied using HDL subjected to heparin-agarose affinity chromatography to remove apoprotein (apo) E and B. Saturation curves for binding of apo E-free 125I-HDL showed at least two components: low-affinity nonsaturable binding and high-affinity binding that saturated at approximately 20 micrograms HDL protein/ml. Scatchard analysis of high-affinity binding of apo E-free 125I-HDL to normal fibroblasts yielded plots that were significantly linear, indicative of a single class of binding sites. Saturation curves for binding of both 125I-HDL3 (d = 1.125-1.21) and apo E-free 125I-HDL to low density lipoprotein (LDL) receptor-negative fibroblasts also showed high-affinity binding that yielded linear Scatchard plots. On a total protein basis, HDL2 (d = 1.063-1.10), HDL3 and very high density lipoproteins (VHDL, d = 1.21-1.25) competed as effectively as apo E-free HDL for binding of apo E-free 125I-HDL to normal fibroblasts. Also, HDL2, HDL3, and VHDL competed similarly for binding of 125I-HDL3 to LDL receptor-negative fibroblasts. In contrast, LDL was a weak competitor for HDL binding. These results indicate that both human fibroblasts and arterial smooth muscle cells possess specific high affinity HDL binding sites. As indicated by enhanced LDL binding and degradation and increased sterol synthesis, apo E-free HDL3 promoted cholesterol efflux from fibroblasts. These effects also saturated at HDL3 concentrations of 20 micrograms/ml, suggesting that promotion of cholesterol efflux by HDL is mediated by binding to the high-affinity cell surface sites.