Raynaud's phenomenon is a disorder whereby blood vessels in the fingers and toes constrict and reduce blood flow, causing pain and discolouration. This is usually in response to cold exposure or emotional stress. In a small number of cases, Raynaud's phenomenon is associated with an underlying disease but, for most people, it is idiopathic (of uncertain cause, or 'primary'). Primary Raynaud's phenomenon is extremely common (especially in women), with one UK study suggesting that over 15% of the population are affected.
For people with primary Raynaud's phenomenon who do not respond to conservative measures (e.g. keeping warm), calcium channel blockers represent the first line in drug treatment. Calcium channel blockers (sometimes called calcium antagonists) are drugs that affect the way calcium passes into certain muscle cells and they are the most commonly prescribed medication for primary Raynaud's phenomenon.
This review examined seven randomised trials which included 296 participants. Although overall all the trials were classed as being at low or unclear risk of bias, the sample size of the included trials was small and there was unclear reporting of outcomes. Two different calcium channel blockers were included: nifedipine and nicardipine. Comparisons in six trials were with placebo and in one trial with both placebo and another type of drug (although only data relating to the calcium channel blocker and placebo were used in this case). Treatment with oral calcium channel blockers was found to be minimally effective in primary Raynaud's phenomenon, reducing the frequency of attacks by around 1.7 attacks per person per week. One trial provided information on duration of attacks reporting no difference between the calcium channel blocker and placebo groups. Oral calcium channel blockers had no effect on severity scores in those trials in which these were assessed. Only two trials reported preference scores (whereby participants are asked which treatment they prefer) specifically in those with primary Raynaud's phenomenon, and in only one of these was there a between-treatment group difference (participants preferred nifedipine to placebo). Physiological measurements (for example measurement of finger blood flow) were performed in five trials, with no differences found between calcium channel blocker and placebo treatment. Treatment with calcium channel blockers was associated with a number of adverse events including headaches, flushing and ankle swelling. The results of this review were, however, limited by the low number of participants recruited to the studies and by the limitations of currently used outcome measures.