Low-dose anticholinergic therapy causes cognitive impairment in Parkinson's disease patients

Background: Before L-Dopa’s discovery, anticholinergic drugs were among the first treatments for Parkinson’s disease. Only now trihexyphenidyl (THP) is approved to treat unresponsive L-dopa tremors in young, cognitively unaffected Parkinson’s disease patients. However, there are no specific recommendations for disease duration, medication dose, or cognitive status. In low-income countries, THP is still frequently used in Parkinson’s disease patients with tremor. The objective of the current study was to evaluate cognitive performance in Parkinson’s disease patients receiving a low dose of THP. Material and methods: The study was performed on nineteen PD patients, nine of whom were on THP. All patients completed MoCA cognitive assessment. The patients were matched depending on their age, disease severity based on UPDRS III and duration of the disease. Results: The THP patients were taking an average dose of 3.3 mg of THP daily for an average of 1.8 years. There were no statistical differences between THP patients and non-THP patients in age (64.8± 4.8 vs 67.2±6.9, p=0.4), UPDRS III (32.1±8.9 vs 41.5±20.6, p=0.2) and disease duration (6.2±4.9 vs 7.0 ± 4.0, p=0.7). The THP patients had lower cognitive performance, with a total MoCA of 19.22 ± 3.3 vs. non-THP patients 24.2±3.0, p=0.003. Conclusions: In Parkinson’s disease patients, even a low dose of THP causes significant cognitive loss.