Guanethidine Sulfate is a medication used to treat high blood pressure (hypertension). It works by blocking the release of norepinephrine, a neurotransmitter that can increase blood pressure by constricting blood vessels. Guanethidine Sulfate is classified as a sympatholytic agent, which is a type of medication that reduces sympathetic nervous system activity. It is available in tablet form for oral administration and is usually prescribed by a doctor. Guanethidine Sulfate is typically reserved for cases of hypertension that are resistant to other medications.