"I currently take co-careldopa (Sinemet), memantine (Namenda) and quinine."
Thank you so much for asking this question since drug interaction with cannabis must be addressed but I want to answer this for your benefit as well as for other patients that may have questions about their medication interacting with cannabis.
There is a great web site that will give you the drug interaction information you are seeking:
https://www.drugs.com/drug-interactions/cannabis.html. Cannabis drug interactions are listed and you will find 4135 brand name interactions and 580 moderate interactions with 7 major drug interactions from 31 brand and generic names.
If you still are uncertain if there is a potential interaction you may look at the metabolism and if the medication is metabolized by the cytochrome P450 enzymes, there is potential interaction. This web site will give you the interaction of your medication with cannabis if you ask but it will also inform you of other potential interactions with your medications.
We do know that cannabis does affect the dopamine system in the body and heavy cannabis may significantly alter the brains dopamine system. This web site does not distinguish between THC and CBD effects or interactions.
The effects of cannabis on Parkinson’s disease patients is variable but it helps to support the endocannabinoid system with CBD. Low dopamine levels in Parkinson’s disease may be preexisting or a result of heavy, long term cannabis use, especially the THC without the balance of CBD to protect the brain.
There are still so many questions we do not have answers for at this time and further studies must be done but at least you may check on your drug to drug interactions and that shows wisdom that you recognize the importance of knowing your medications.