Effect of plasma proteins on buprenorphine transfer across dually perfused placental lobule.

OBJECTIVE

The aim of this investigation is to determine the effect of human serum albumin (HSA) and alpha-acid glycoprotein (AAG) on buprenorphine (BUP) transplacental transfer and distribution.

METHODS

The technique of dual perfusion of placental lobule (DPPL) was utilised. BUP was co-perfused with the marker compound antipyrine (AP). In each experiment, the radiolabelled isotopes [(3)H]-BUP and [(14)C]-AP were added to enhance their detection limits. Human plasma proteins, HSA and AAG, were added to both the maternal and fetal circuits separately and in combination at their physiological concentrations in maternal and fetal circulations close to term.

RESULTS

Transplacental transfer of BUP, in absence of plasma proteins, is a two-step process: the first is its uptake by the syncytiotrophoblast from the maternal circuit, and the second is its transfer/release from the tissue to the fetal circuit. The addition of HSA to the perfusion medium affected only the second step of BUP transfer, but AAG affected both steps. The combined effect of HSA and AAG was not different from that observed in presence of the latter alone.

CONCLUSIONS

Binding of BUP to circulating AAG could have an important role in the transfer of the drug from the maternal to fetal circulation.