Hold on, how do you know you have "excess dopamine"?
Licorice root contains many compounds that could affect you (I'm unfamiliar with this plant, but our fellow member @Gamesguru should have more information for you) - how do you know it's inhibition of Dopamine synthesis that's helping you? For instance... I just found this quick article, which claims that Licorice contains an MAOI-like compound, which increases dopamine activity...!
Antidepressant-like activity of Glycyrrhiza glabra L. in mouse models of immobility tests.
https://www.ncbi.nlm...pubmed/16443316
This suggests that antidepressant-like effect of liquorice extract seems to be mediated by increase of brain norepinephrine and dopamine, but not by increase of serotonin.
Now, I also see some articles about how it contains a compound which does the opposite - blocks dopamine activity.
https://www.scienced...90218223504.htm
However, don't go off too fast on the idea that you need to lower dopamine activity or synthesis - the effects of licorice is obviously a lot more complex than just that - and it seems to me, that it MODULATES dopamine activity, rather than just lower or increase it.
If you're absolutely certain that enhanced dopamine synthesis is your issue, or increased dopamine activity (this implies something like hyperthyroidism... which is actually often fixable with surgery or other measures), then you can always go on a Tyrosine elimination-diet.
https://en.wikipedia...nts_and_sources
Eliminate the most potent sources, and you will put a very big stop to the production of dopamine - it will still be synthesised through other pathways, but this will lower it significantly.
If you want to go hardcore drugs, then the third-generation antipsychotics is the way to go: Aripiprazole (lowers prolactin, hence probably won't lower T), Brexpiprazole and Cariprazine. Personally I would probably do that - it's actually a more selective approach than eliminating dopamine entirely.