Step 1: Define menorrhagia. It is heavy menstrual bleeding (excessive amount or duration of menstrual flow), commonly managed medically before considering surgery.
Step 2: List the evidence-based medical options. Tranexamic acid (antifibrinolytic) and NSAIDs reduce blood loss; combined oral contraceptive pills regulate and lighten flow; and progestogens (oral or the levonorgestrel intrauterine system) thin the endometrium and reduce bleeding. All have good evidence.
Step 3: Evaluate ethamsylate. Ethamsylate is a hemostatic agent claimed to act on capillaries, but controlled trials have shown it to be ineffective at meaningfully reducing menstrual blood loss, so it is NOT an evidence-based treatment.
Step 4: Apply the exception logic. The question asks which is NOT evidence-based; that is ethamsylate.
Step 5: Confirm. Tranexamic acid, OCPs, and progesterone all have demonstrated efficacy, leaving ethamsylate as the answer.
Hence the answer is ethamsylate.