I'm not sure, if this will help or not. I found in my my experimentation with mucuna and sinemet, is that you can't dramatically change your meds (whatever it might be) from one day to the next. You really have to make changes gradually (weeks not days). These are all powerfull drugs, his body needs time to adjust.
I know of couple PD'ers taking Lodosyn & mucuna together with great results. I live in Canada, and Lodosyn is not available here, otherwise I would use it instead of sinemet.
Have him keep a detailed record of what, how much and when he takes these meds. Also when it kicks in, how long it lasts. I find, for me, mucuna works best on an empty stomach.
I was diagnosed with pd 7 years ago, been taking mucuna and a little bit of sinemet for 15 months now with terrific results.

Take care and good luck. Max