Hello, I have gone through your query and understand your concern. You can take Suprep. There is much confusion regarding allergy to sulfa-containing drugs, Sulfa, Sulfites, Sulfates and Sulfur. Sulfa allergies are common from medications. Originally the name is from a class of drugs known as sulfonamides but these do differ from medications/foods which contain added sulfites or sulfates. Therefore a patient which is affected by sulfa allergies usually is not affected by the added sulfur-containing drugs, foods or additives or sulfate containing products like ferrous sulfate, magnesium sulfate etc. To date there is no known difficulties any patients seem to show to this group of compounds so a sulfa allergy or a sulfite sensitivity patient should have no problems with magnesium sulfate. However one trial of the drug or skin allergen test can help in establishing the allergic response. As they are the salts of potassium, Sodium and Magnesium and their ions may lead to electrolyte imbalance if you take excess than prescribed. Further it is better to check these electrolytes level and Electrocardiogram before using suprep as you have supra ventricular tachycardia. Hope this helps. Please write back for further queries. wishing you good health.