Question about Medicinal Patents.....

Let' say there's a patented Medicine on the market having 10 ingredients in the patent.

If I add 1 or 2 extra ingredients to make it more effective, can I now patent that, or do I need to get a license from the original patent holder?

Planning on putting a anti-cancer herbal ayurvedic formulation together and get the formula patented, however after doing a google search I found that there is something similar already patented, but mine has more ingredients. So im on here to see what the consensus is on this ordeal before I start looking for any patent lawyers or doing it myself.

Thanks guys