Design of a
liposome delivery system for
vaginal administration of
acyclovir, able to provide sustained release and improved bioavailability of the encapsulated
drug for the local treatment of
genital herpes was investigated.
Acyclovir was encapsulated in
liposomes prepared by the
polyol dilution method, whereby various
phospholipid compositions were used: egg phosphatidylcholin (PC)/egg
phosphatidylglycerol (PG) 9:1, egg
phosphatidylcholine (PC) and egg phosphatidycholine (PC)/
stearylamine (SA) 9:3. All
liposome preparations were characterized and compared for particle size, polydispersity, encapsulation efficiency and tested for in vitro stability in different media chosen to simulate human vaginal conditions:
buffer, pH 4.5 (corresponding to normal human vaginal pH), vaginal fluid simulant (medium developed so as to mimic the fluid produced in the vagina) with or without
mucin. To be closer to in vivo application of
liposomes and to achieve further improvement of their stability,
liposomes were incorporated in a vehicle suitable for vaginal
self-administration. Bioadhesive
hydrogel made from
Carbopol 974P NF resin with adequate pH value and desirable viscosity was chosen as a vehicle for
liposomes containing
acyclovir. In vitro release studies of
liposomes incorporated in the
hydrogel proved their applicability as a novel vaginal delivery system with localized and sustained release of encapsulated
acyclovir. Even after 24 h of incubation in vaginal fluid simulant more than 35% of the originally encapsulated
drug was retained in the
hydrogel.