HPLC Comparison of Dopamine in Parkinson's Therapy

Two common drug combinations used to treat Parkinson's disease are levodopa with carbidopa and entacapone (LCE) and levodopa with benserazide (LB). Both work by boosting the availability of dopamine in the brain to help improve movement-related symptoms, but how they compare in terms of their short-term effects on dopamine levels in the blood is not yet fully understood. A joint study by researchers atAtatürk Sanatoryum Training and Research Hospital and Ankara University Medicine Faculty (both in Ankara, Turkey) set out to compare the two treatments in patients with early-stage Parkinson's disease affecting one side of the body. Blood samples were taken from participants before they took their medication and again at 90 and 180 minutes afterwards, and dopamine levels were measured using high-performance liquid chromatography (HPLC). A paper based on this research was published in the journal Medicine.¹

How and Why is Levodopa Used to Treat the Movement Symptoms of Parkinson's Disease?

The movement problems seen in Parkinson's disease happen because the brain loses cells that produce dopamine in a key area called the striatum. That's why the best treatments focus on either boosting dopamine levels in the brain or tricking the brain into thinking it has enough. The most common medication is levodopa, which the body converts into dopamine, both in the brain and elsewhere in the body.^2-5 Levodopa is broken down in the body by two main enzymes before it can reach the brain. To make sure more of it gets where it needs to go (and to reduce side effects) it's usually taken alongside other medications that block this breakdown process in the body. Common combinations include levodopa paired with benserazide, or levodopa combined with two blockers at once. These combinations have proven to be both effective and well-tolerated in helping control the movement symptoms of Parkinson's disease.⁶

Do LCE and LB Differ in How Much They Raise Dopamine Levels in the Blood in Early-Stage Parkinson's Patients?

For this study, patients were recruited who had been diagnosed with early-stage Parkinson's disease affecting one side of the body and randomly assigned them to receive one of the two drug combinations. Ninety patients took part, just over a third of whom were female, with a median age of 69.5 years. The vast majority had the tremor-dominant form of the disease. Roughly half received LCE and half received LB. Both treatments led to a rise in dopamine levels in the blood within the first three hours. However, when the two groups were compared, there was no meaningful difference between them in terms of how much dopamine levels increased, either between the groups or within each group over time.¹

“These findings,” write the authors of the paper,¹ “suggest that both medications may exert similar effects on dopamine metabolism. Moreover, the fact that the patients included in our study were in the early stages of the disease, had unilateral involvement, and the use of low-dose levodopa may have contributed to the limited changes observed in dopamine levels. This implies that in the early stage of Parkinson’s, when progressive neuronal loss has not yet begun and dopamine reserves are still preserved, biochemical differences between levodopa combinations may not yet become apparent.”

The researchers believe that larger studies involving multiple hospitals and longer follow-up periods will be needed to fill the remaining gaps in our understanding of this area.¹

Read More on Similar Topics

Non-Invasive Detection of Parkinson’s Disease: VOC Profiling Using Chromatography and Mass Spectrometry

References

1. Korucu, O.; Özdemir, S.; Türkeş, G. F. et al. Comparison of Blood Dopamine in Parkinson's Patients Treated with Levodopa Carbidopa Entacapone vs Levodopa Benserazide: A Randomized Controlled Trial. Medicine (Baltimore) 2026, 105 (21), e48895. DOI: 10.1097/MD.0000000000048895
2. Ebada, M. A.; Alkanj, S.; Ebada, M. et al. Safety and Efficacy of Levetiracetam for the Management of Levodopa-Induced Dyskinesia in Patients with Parkinson’s Disease: A Systematic Review. CNS Neurol Disord Drug Targets 2019, 18, 317–325. DOI: 10.2174/1871527318666190314101314
3. Sisodia, V.; Dubbeld, L.; De Bie, R. M. A. et al. Efficacy and Safety of Adjunctive Oral Therapy in Parkinson’s Disease with Motor Complications: A Systematic Review and Network Meta-Analysis. BMJ Neurol Open. 2024, 6, e000573. DOI: 10.1136/bmjno-2023-000573
4. Pauls, K. A. M.; Toppila, J.; Koivu, M. et al. Polyneuropathy Monitoring in Parkinson’s Disease Patients Treated with Levodopa/Carbidopa Intestinal Gel. Brain Behav. 2021, 11, e2408. DOI: 10.1002/brb3.2408
5. Tanner, C. M.; Ostrem, J. L. Parkinson’s Disease. N Engl J Med. 2024, 391, 442–452. DOI: 10.1056/NEJMra2401857
6. Foltynie, T.; Bruno, V.; Fox, S. et al. Medical, Surgical, and Physical Treatments for Parkinson’s Disease. Lancet 2024, 403, 305–424. DOI: 10.1016/S0140-6736(23)01429-0