Bicisate

The neutral and lipophilic nature of bicisate provides it with high stability. This property is given by its N2S2 core. This characteristic has been proven to allow bicisate to be used even several hours after preparation and to present an easy passage through the blood-brain barrier.

Bicisate is rapidly uptaken by the brain. The retention of bicisate in the brain is associated with stereospecific de-esterification to hydrophilic acid derivatives. Even though both DD and LL isomers demonstrate brain uptake, only the LL presents brain retention. Bicisate brain localization is performed by passive diffusion and the presence of slow hydrolysis in the blood and rapid hydrolysis in the brain. The hydrolysis of bicisate forms the monoacid and diacid bicisate derivatives. The formation of these derivatives results in high brain uptake and retention. The uptake of bicisate depends on the blood flow directed to the brain and thus the presence of a stroke will be translated into specific zones in the brain that would not include the complex of bicisate and technetium Tc-99m.

The stability of bicisate is superior when compared to other brain radiopharmaceuticals. Thus, the reported half-life of bicisate is of 6.02 hours. When broadly studied in clinical trials, the pharmacokinetic profile fits a three-compartment model with half-lives of 43 seconds, 49.5 minutes and 533 minutes.

After intravenous administration, bicisate presents a very large brain extraction. About 5% of the administered dose remains in the blood one hour after administration. The highest concentration of radioactivity in blood was attained 0.5 minutes after intravenous injection and it represented 13.9% of the injected dose. After intravenous administration of bicisate, the permeability surface area was 0.48 ml.g/min.