A 34-year-old woman presents with heavy menstrual bleeding (HMB). Her periods last 7-10 days, and she needs to change protection every 1-2 hours on the heaviest days, passing clots. She is otherwise well. Examination is unremarkable. Initial investigations (FBC, coagulation screen, thyroid function) are normal. She does not desire pregnancy currently. According to NICE NG88, what is the first-line pharmacological treatment option if hormonal contraception is not desired or suitable?