The Effect of Oral Magnesium Pidolate on Incidence of Painful Crises in Patients With Hemoglobin SC Disease

This is a placebo-controlled study which means that the effectiveness of the magnesium medication (the chemical form of which is known as Mg pidolate) will be compared to placebo. A placebo looks like the drug that is being studied (in this case magnesium) but does not contain any active drug of any kind. Comparing magnesium with placebo will help decide whether magnesium is better than treatment with placebo.

The study lasts for 64 weeks (about 16 months) and is divided into 2 parts, each part lasting for 32 weeks (8 months). During the first part study medication (magnesium or placebo) will be taken twice daily for 24 weeks (about 6 months), followed by no study medication for 8 weeks. These 8 weeks are called a washout period, during which time the effects of the study medication are 'washed-out' of the body. After the washout 8 weeks, patients will enter the second part of the study. During this second part, the study medication (magnesium or placebo) will again be taken twice daily for 24 weeks. During the second part of the study participants will receive whichever study medication that was not taken during the first part of the study. Following the second 24 weeks, there will be an observation period of 8 weeks (during which time no study medication is taken). The study is completed at the end of the 8-week observation period. Participants will take magnesium for 24 weeks and placebo for 24 weeks. The decision whether participants will receive magnesium or placebo first will be made randomly by a computer. This is a double-blind study which means that neither the participant nor the study doctor will know which study medication is taking during each part of the study. However, the study may be unblinded for safety issues if necessary.

If the participant responds to the study medication, it can be continued after completion of the 24 weeks.

The study medication is in the form of a liquid, taken two times a day (morning and evening) with the actual amount taken depending on the participant's weight.

During this study the participant will be seen in clinic on a regular basis; initially every 2 weeks, later once a month. There will be a total of 21 clinic visits during the study. Three of these are clinic visits that would normally take place in the routine management of this disease. The other 18 visits are required for this study. At each visit participants will have blood tests to measure the amount of magnesium in the blood, especially the red blood cells, but also to look for any other changes that might occur. The total amount of blood collected during the 16 month study is 120 ml (24 teaspoons), which is a safe amount. Three ml (half teaspoon) will be drawn at 13 visits, 5ml (1 teaspoon) at 4 visits, and 15ml (3 teaspoons) at a further 4 visits. At 4 of the clinic visits a urine test will be performed.