"Acyclovir crosses the blood-brain barrier, a desirable quality for the treatment of herpes encephalitis, neonatal herpes simplex virus infections, and, possibl

"Acyclovir crosses the blood-brain barrier, a desirable quality for the treatment of herpes encephalitis, neonatal herpes simplex virus infections, and, possibly, multiple sclerosis" [0] "The bioavailability of orally administered acyclovir is limited to 15 to 30% (23), and the level of passage across the blood-brain barrier has been assumed to be low, probably due to the relatively low lipophilicity of acyclovir (8). It was previously found (14) that upon oral administration the acyclovir concentration in cerebrospinal fluid (CSF) is only 13 to 52% of that found in plasma. When sustained and high concentrations of acyclovir in plasma are desirable, improved bioavailability can be achieved with valacyclovir, the hydrochloride salt of the l-valyl ester of acyclovir." [1] [0] http://aac.asm.org/content/54/3/1146.full http://aac.asm.org/content/54/3/1146.full [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC166099/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC166099/