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The erectile dysfunction drug sildenafil (Viagra) may also help treat Raynaud's phenomenon, one of the most common complications of limited cutaneous systemic sclerosis.

In a small randomized, double-blinded, and placebo-controlled trial, the drug led to a significant percentage reduction in the number of weekly attacks of Raynaud's phenomenon, according to Ariane Herrick, MD, of the University of Manchester in England, and colleagues.

The absolute number of such attacks was also reduced, but the change did not reach statistical significance, Herrick and colleagues reported in the March issue of Arthritis & Rheumatism.

Raynaud's phenomenon -- which causes tiny blood vessels in the skin to spasm in response to cold temperatures or stress -- occurs in almost all cases of scleroderma, an autoimmune disease, the researchers noted.

These spasms can lead to serious complications, including digital ulceration, soft tissue or bone infection, and gangrene.

Sildenafil -- a phosphodiesterase type V inhibitor -- produces smooth muscle relaxation in blood vessels, which accounts for its effects in many cases of erectile dysfunction and also in pulmonary arterial hypertension.

It's "attractive" in systemic sclerosis because of its potential to counter the spasms characteristic of Raynaud's phenomenon, the researchers wrote, although previous research has yielded mixed results.

To test the issue, Herrick and colleagues gave 57 patients with the condition 100 milligrams of sildenafil once a day for three days, followed by either 200 milligrams of the drug once a day or an identical placebo for 25 days.

The sildenafil was in a modified-release formulation to allow once-daily dosing, they noted, and for this study, Raynaud's phenomenon was defined as episodic digital pallor followed by cyanosis, erythema, or both in response to cold or emotion.

The primary endpoint was the percentage change in the weekly frequency of Raynaud's attacks -- to be eligible for the study, patients had to begin with a frequency of at least seven attacks a week on five or more days.

Secondary endpoints included change in the absolute number of attacks, the Raynaud's Condition Score, the duration of attacks, the pain score, endothelial dysfunction, and serum biomarker levels.

Herrick and colleagues found:

• On average, patients in the sildenafil group had a 44% reduction in the frequency of attacks per week, compared with 18.1% for those in the placebo group.
• The difference was significant at P=0.034.
• The average number of attacks also improved -- from 30.5 at baseline to 18.7 after sildenafil treatment, compared with 25 at baseline to 19.3 in the placebo group.
• But that difference did not reach significance (at P=0.244).
• Changes in several other endpoints also appeared to favor the drug, but did not reach significance.

Herrick and colleagues reported that patients taking sildenafil had more adverse events than those in the placebo group, but they were mostly mild or moderate.

The researchers cautioned that the study was small and did not have sufficient statistical power to detect in secondary efficacy endpoints. As well, they noted, 33% of the patients treated with the drug were excluded from the efficacy analysis for protocol violations, which might have biased the results.

The modified-release formulation might also not have provided the most effective dose, they added.

On balance, they concluded, the data suggest that the drug might make a useful addition to treatment options for Raynaud's phenomenon secondary to limited cutaneous systemic sclerosis.

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