Senna (Sanā)
السنا
Preparation: Seven leaves of senna steeped in warm water overnight, strained and drunk on empty stomach. For acute poisoning with retained toxic matter in digestive tract.
Duration: Single dose for acute episode, may repeat after 12 hours if evacuation incomplete
Source: Ibn al-Qayyim, At-Tibb an-Nabawi, Chapter on the Benefits of Plants Mentioned by the Prophet - describes senna as a powerful purgative specifically for eliminating harmful substances from the intestines, citing the hadith 'Use senna and sanoot for indeed in them is cure for every disease except death' (Sunan Ibn Majah 3457, Hasan)
