If they don’t have an FDA license (which I doubt), then send a pill (or a random selection from different batches, if they have batch codes) to a lab and have it tested for contaminants. I doubt the manufactureres have many QA practices and whether they follow GMP or GLP is another matter. And even if they say their product is good …

http://www.usatoday.com/news/health…axy-drugs_N.htm