In conventional medicine, new medicines (sources are mostly chemical/synthetic) are constantly being created, tested in test-tubes, sick persons, or animals (rats), and going in and out of market every few years once their side effects become obvious to the general public. How many conventional drugs of yesterday can be found on the chemists' shelves today? They all had their day, and their alluring names have faded into oblivion (because they are declared ineffective or dangerous), only to be replaced by newer drugs.
Homeopathic medicines (prepared from many natural substances such as herbs and minerals) used in the times of Dr. S. Hahnemann (200 yrs back) are used even today because of their efficacy. They have been tried and tested on healthy human beings. They are known, trusted, and reliable.