Are levodopa preparationas with benserazide and carbidopa clinically equivalent?

Parkinson’s disease is the only neurodegenerative disease that can be effectively treated symptomatically. Treatment of motor symptoms is based primarily on the use of drugs that increase the activity of the nigrostriatal dopaminergic system and compensate for dopamine deficiency. Levodopa remains the gold standard of dopaminergic therapy. It is the most effective and best tolerated anti-parkinsonian drug, it causes the fewest side effects, also in the elderly patients. Oral preparations of levodopa additionally contain one of the aromatic L-amino acid decarboxylase inhibitors: benserazide or carbidopa. Inhibitors have a beneficial effect on the bioavailability of levodopa in the central nervous system, its clinical efficacy and tolerability. In practice, according to common opinion, the preparations of levodopa with carbidopa and levodopa with benserazide are clinically equivalent and can be used interchangeably. The case of a 69-year-old patient treated for 6 years for Parkinson’s disease is presented. The patient presented motor symptoms of advanced Parkinson’s disease: wearing-off motor fluctuations and peak dose dyskinesia. The was treated with levodopa in a dose of 5 × 200 mg (preparation of levodopa with benserazide) as a monotherapy. Due to the worsening availability of the drug used so far in pharmacies, it was changed to a preparation containing levodopa and carbidopa, while maintaining the same dose of levodopa. During the next visit, the patient reported that the change of the formulation had a beneficial effect in the form of a slight but significant reduction in the incidence and severity of peak dose dyskinesia. Pharmacokinetic studies showed that the mean maximum concentration of levodopa after administration of levodopa + benserazide was significantly higher than after administration of levodopa + carbidopa. The preparation containing benserazide caused a rapid increase and then a rapid decrease of the lewodopa plasma concentration. When levodopa was combined with carbidopa, the concentration of levodopa increased and decreased slowly. The results of these pharmacokinetic studies may explain the patient’s observation of the amelioration of peak dose dyskinesia after switching from a levodopa + benserazide formulation to a levodopa + carbidopa combination.