If you have a doctor's prescription, you can go to the local hospital pharmacy or drugstore to buy it. Generally speaking, it should be for sale. If you can't buy it at a local pharmacy, you can go to a large chain pharmacy or buy it through an online pharmacy.
However, it should be noted that the purchase of medical drugs must be formal, and qualified pharmacies or platforms should be selected as far as possible to ensure the quality and safety of products. In addition, according to local laws and regulations, some drugs may need prescriptions to be purchased, and relevant preparations need to be made in advance.