Are vitamin B6 blood levels affected by levodopa/carbidopa therapy in patients with Parkinson’s disease?

This study investigated the role of levodopa/carbidopa (LC; Sinemet) therapy on vitamin B6 levels in patients with Parkinson's disease (PD). Researchers suggested that vitamin B6 might have an important role in Parkinson’s disease and its levels might be affected by LC therapy.

PD affects brain cells which lose their abilities to control body functions. Patients with PD lose their control over body movements and experience symptoms such as tremors.

The first-line recommended treatment for these patients is levodopa or LC combinations. Vitamin B6 is required for the activation of LC once it enters the body. Long-term LC might lead to vitamin B6 levels drastically decrease. This may also result in impaired LC therapy effectiveness among other risks. However, the levels of vitamin B6 in patients with PD are usually not included in their routine testing. The effects of vitamin B6 levels in patients with PD treated with LC are not well known.

This study included information about 24 patients treated with LC for 3 or more years. 6 patients received intraduodenal (through the intestine) LC intestinal gel and 18 patients received LC tablets. Vitamin B6 blood levels were assessed.

All 6 patients treated with LC intestinal gel and 13 of the 18 patients treated with LC tablets had low levels of vitamin B6. 8 of the 19 patients with low vitamin B6 blood levels experienced symptoms of low B6. These symptoms included sore tongue and gums, and anemia.

On average, patients with low vitamin B6 levels have been treated with larger doses of LC in the year before. However, these changes were not significant. Patients treated with the LC intestinal gel had significantly lower levels of vitamin D compared to those receiving LC tablets. 

This study concluded that vitamin B6 blood levels might play an important role in LC therapy effectiveness in patients with PD. Also, LC therapy may influence vitamin B6 blood levels.

This study included a limited number of participants. Therefore, further studies with a bigger population are necessary. Also, this study was based on medical records. Some information might have been incomplete which can affect the results.