Levodopa (LD) is the most effective antiparkinsonian drug used in the treatment of Parkinson disease (PD). Sex differences in the bioavailability of LD have been shown previously. In addition, epidemiological sex differences in PD have been reported, suggesting an involvement of estrogen. In this study, we evaluated the pharmacokinetics of LD in elderly patients with PD to examine the influence of estrogen.
After the oral administration of a tablet of LD 100 mg/carbidopa 10 mg in 128 PD patients (including 91 elderly patients; age at examination, 75 years or older), plasma LD concentrations were measured at 6 points until 180 minutes, and pharmacological parameters were calculated. Then, differences in these parameters between sex were compared.
The area under the curve (AUC) and the AUC adjusted for body weight were found to be significantly greater in the female subjects compared with the male subjects (P < 0.0001 and P < 0.0001, respectively). Furthermore, in the elderly patients, the AUC and the AUC adjusted for body weight were significantly greater among the female subjects (P < 0.0001 and P < 0.0001, respectively).
Even in the elderly cohort, the women had a significantly greater bioavailability of LD. In conclusion, to avoid the development of motor complications during LD treatment, it is important to consider the sex differences in the bioavailability of LD.