The currently commonly used compounded dobutamine contains either carbidopa or benserazide as an adjunctive ingredient. The main indications for carbidopa and benserazide are to treat gastrointestinal reactions such as nausea due to the administration of 3,4-dihydroxyphenylalanine (L-DOPA), to reduce the degradation of levodopa, and to increase the efficacy. Recent studies have found that both drugs irreversibly bind and continuously inactivate pyridoxal 5′-phosphate (PLP) PLP-dependent enzymes. PLP is the active form of vitamin B6. PLP is required for the function of over 300 enzymes and proteins. The major systems in the body are directly or indirectly affected by PLP. Therefore taking carbidopa or benserazide may cause disorders of nutrient metabolism. It is necessary for patients with Parkinson’s disease taking compounded dopa drugs to take appropriate vitamin B6 supplementation to avoid possible vitamin B6 deficiency, which may lead to malnutrition. Weight loss and malnutrition in patients with Parkinson’s disease may be associated with vitamin B6 deficiency.