Effect of Calcium-Channel Blockade on the Cold-Induced Vasodilation Response

Introduction: Cold-induced vasodilation (CIVD) is seen in the extremities during exposure to cold. A strong vasodilation response has been associated with a decreased risk of cold injury. Increasing CIVD might further decrease this risk. The calcium-channel blocker nifedipine causes vasodilation and is used to treat Raynaud's syndrome and chilblains. Nifedipine is also used for high altitude pulmonary edema and could potentially serve a dual purpose in preventing frostbite. The effects of nifedipine on CIVD have not been studied.

Methods: A double-blind crossover study comparing nifedipine (30 mg SR (sustained release) orally twice daily) to placebo was designed using 2 sessions of 4 finger immersion in 5°C water, with 24 h of medication pretreatment before each session. Finger temperatures were measured via nailbed thermocouples. The primary outcome was mean finger temperature; secondary outcomes were mean apex and nadir temperatures, first apex and nadir temperatures, subjective pain ranking, and time of vasodilation onset (all presented as mean±SD).

Results: Twelve volunteers (age 29±3 [24-34] y) completed the study. No significant difference in finger temperature (9.2±1.1°C nifedipine vs 9.0±0.7°C placebo, P=0.38) or any secondary outcome was found. Pain levels were similar (2.8±1.6 nifedipine vs 3.0±1.5 placebo, P=0.32). The most common adverse event was headache (32% of nifedipine trials vs 8% placebo).

Conclusions: Pretreatment with 30 mg of oral nifedipine twice daily does not affect the CIVD response in healthy individuals under cold stress.

Keywords: calcium channel blockers; cold injury; environmental medicine; prevention and control.