This is why Dr. Marty Hinz's methodology of treatment prescribes the use of 5-htp for control of Serotonin depletion through competitive inhibition at the AADC enzyme by 5-htp and L-dopa. With increasing L-dopa administration, you get less enzyme activity by 5-htp, reducing the amount of Serotonin being produced leading to less being available in the pre-synaptic vesicles and then ultimately in the synaptic cleft when post synaptic activation is required. 5-htp use in the treatment of Parkinsons disease can also control nausea, which is the main dosage limiter as patients will experience intolerable nausea once the L-dopa gets high enough which will create a dosage barrier than cannot be overcome until it is resolved. The current resolution for this issue presently is Carbidopa, but it comes with a myriad of side effects. If 5-htp is able to resolve nausea just as well, if not better, as well as preventing Serotonin depletion, leading to resolution of L-dopa side effects like depression, then it is clearly the superior option. Carbidopa also decreases the effectiveness of L-dopa as it depletes Vitamin B6 which is a co-factor in the conversion of L-dopa to Dopamine.