Calcium is considered a vitamin or supplement. It is available over the counter, so it is most likely legal for sale as you describe. Whether the products you purchased are legal for sale in the U.S. would require someone to review the product, labeling, etc.
You could try contacting the FDA.
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Based on your description, I am not clear if the "medicine" you are referring to is a pharmaceutical drug, or something else. Also, the fact that it was imported by a foreign company does not necessarily mean it is not proper for US sale. Why don't you contact the seller and ask them to answer your questions.
Perhaps, you should contact the United States Food & Drug Administration and make inquiry.
I hope this is helpful.
John N. Kitta
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