A Cochrane review included 3 studies with a total of 524 subjects. The first study tested the effectiveness of zinc sulphate to prevent sickle cell-related crises in a total of 145 participants. The patients recruited from a haematological clinic in India were aged between 12 and 27 years. Zinc sulphate 220 mg three times a day orally reduced significantly the total number of pain, haemolytic, aplastic and sequestration crises over one and a half years, WMD -2.83 (95% CI -3.51 to -2.15). Changes to red cell parameters and blood counts were inconsistent. No serious adverse events were noted in the study.
The second study (n=90) was a Phase II dose-finding study of senicapoc (Gardos channel blocker) compared to placebo. Compared to the placebo group the high dose senicapoc showed significant improvement in change in hemoglobin level, number and proportion of dense red blood cells, red blood cell count and indices and hematocrit. The results with low-dose senicapoc were similar to the high-dose senicapoc group but of lesser magnitude. There was no difference in the frequency of painful crises between the three groups. A subsequent Phase III study (n=289) of senicapoc was terminated early since there was no difference observed between the treatment and control groups in the primary end point of painful crises.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals) and by study quality (inadequate follow up).