A 42-year-old woman presents with heavy menstrual bleeding, reporting soaking through pads every 1-2 hours during the heaviest days. She is otherwise well. Examination is unremarkable. FBC shows mild anaemia (Hb 110 g/L). Ultrasound scan reveals a normal uterus and ovaries. According to NICE NG88, what is the first-line pharmacological treatment option if hormonal contraception is not desired or suitable?