[Intranasal absorption of rivastigmine hydrogen tartrate and brain targeting evaluation]

To investigate factors influencing the intranasal absorption of rivastigmine hydrogen tartrate (RHT), we studied the pharmacokinetics of RHT after intranasal administration and evaluated its brain targeting behavior. In situ rat nasal perfusion model was used in the study and pH impact was examined on the intranasal absorption of RHT. High performance liquid chromatography (HPLC) method was established to measure RHT concentration in the plasma and brain tissue after intranasal and intravenous administration. The pharmacokinetic parameters, drug targeting index(DTI), and nose-to-brain direct transport percentage (DTP) were calculated. It was demonstrated that the intranasal absorption mechanism of RHT was passive diffusion. The absorption rate was highest at pH 6.0. The absolute bioavailability of intranasally administrated RHT was 73.58%. Compared with that of intravenous administration, RHT absorption into the brain was faster and more efficient after intranasal delivery, and the DTI value was 195.27% of intravenous injection. Moreover, 48.79% of the drug can be absorbed directly from the nose into the brain without systematic circulation. Meanwhile, drug elimination half-time in the brain was prolonged by 1.4 fold compared to that of intravenous injection. In conclusion, intranasal administration of RHT not only improves drug absorption into the system, but also enhances drug absorption rate and content in the brain remarkably, which is an advantage in the treatment of central nervous system-related diseases.