Natrilix SR contains indapamide, which is a sulfonamide-derived medication. Because you have a sulfa allergy, there is a potential risk of an allergic reaction, although the risk of cross-reactivity between sulfa antibiotics and non-antibiotics like Natrilix is generally low. To ensure your safety, do not start taking Natrilix SR yet. Please contact your doctor immediately to inform them of your sulfa allergy. They can easily prescribe a safer, non-sulfa alternative to help lower your blood pressure.