The purpose of this study is to find out whether treatment with magnesium pidolate will increase the amount of water in the red blood cell and result in fewer painful crises in patients with hemoglobin SC disease while not causing diarrhea.

Patients will be randomly assigned to study medication (Mg pidolate or placebo) for 24 weeks, followed by a washout period of 8 weeks. After the washout period each patient will receive a further 24 weeks of study medication.

Inclusion criteria:

This protocol is open to male and female patients of all races with a diagnosis of severe sickle hemoglobinopathy providing they also satisfy the following eligibility criteria:

• Adult and pediatric patients with Hb SC disease who are able to swallow the Mg pidolate preparation and who have had at least one prior painful crisis.

Exclusion Criteria:

• Patients transfused within 90 days of study entry,
• Patients with elevated (>1.5 times upper limit of normal for age) BUN, creatinine, or liver function tests > 3 times the upper limit of normal for age,
• Patients who take a magnesium-containing medication (Mylanta, Maalox, etc.) on a regular (i.e., more than 2 days per week) basis.
• Patients with progressive neuromuscular disease or patients who are treated with a calcium channel blocker.
• Pregnancy

• Texas Children's Hospital
• Children's Hospital Boston