OBJECTIVE RP is a reversible vasoconstriction of digital arteries that causes pain and skin discoloration. This study compared the efficacy of the new phosphodiesterase type 5 inhibitor udenafil with that of the calcium channel blocker amlodipine in the treatment of secondary RP.

METHODS A total of 29 patients with secondary RP associated with connective tissue diseases were enrolled in this double-blind, randomized, cross-over study. The patients were randomized to receive udenafil 100 mg/day or amlodipine 10 mg/day for 4 weeks. After a washout period they were crossed over to the other drug for another 4 weeks. The primary outcome was RP frequency before and after treatment. The secondary outcomes were RP condition scores, RP duration, number of digital ulcers, HAQ, physician global assessment and digital artery flow before and after treatment.

RESULTS Amlodipine and udenafil both decreased the rate of RP attack significantly. The drugs did not differ in terms of RP frequency or any of the secondary outcomes except for digital blood flow; udenafil improved it significantly better than amlodipine (P = 0.021). Udenafil was well tolerated without serious adverse effects.

CONCLUSION Udenafil and amlodipine have comparable efficacy in improving RP attacks. In addition, udenafil improves the blood flow in digital arteries compared with amlodipine.

TRIAL REGISTRATION www.clinicaltrials.gov, protocol number NCT01280266.