Study
Shows Nevirapine (Viramune) Reaches Semen Better than Other NNRTIs or Protease
Inhibitors
By
Liz Highleyman  | Viramune
Tablet |
Earlier
this year the Swiss
Federal Commission for HIV/AIDS sparked controversy when they suggested that
HIV positive individuals on antiretroviral
therapy who are fully adherent, maintain an undetectable viral load (<
40 copies/mL) for at least 6 months, and have no concurrent sexually transmitted
infections essentially cannot transmit HIV through heterosexual vaginal intercourse.
A recent French study, however, found that 5%
of men in serodiscordant couples had intermittently detectable HIV in their semen,
despite meeting the criteria specified in the Swiss statement.
One possible
reason for detectable semen viral load despite undetectable HIV in the blood is
that antiretroviral drugs may fail to reach the genital compartment. Like the
brain, the testes are isolated by a physical barrier that prevents certain substances
-- including many drugs -- from passing through.
At the XVII
International AIDS Conference this month in Mexico City, Australian researchers
presented a poster describing a study looking at how well different antiretroviral
agents penetrate the semen.
Their analysis included data from a cross-sectional
cohort of 119 HIV positive men divided into treated (n= 81) and untreated groups
(n = 38). Participants had well controlled HIV, with undetectable blood viral
load (< 50 copies/mL), a median CD4 count of 595 cells/mm3, and a median treatment
duration of about 30 months.
Blood and semen were collected concurrently
to provide paired samples. The investigators assessed semen viral load using an
assay with a limit of detection of 250 copies/mL. They used high performance liquid
chromatography to measure antiretroviral drug concentrations in the blood and
semen.
Results
•
All treated
individuals had undetectable HIV RNA in both their blood plasma and their semen.
•
Median blood
and semen concentrations for atazanavir
(Reyataz) were 630 mg/L and 87.5 mg/L, respectively (the latter below the
therapeutic concentration of 150 mg/L).
•
Corresponding
concentrations for lopinavir (Kaletra)
were 7428 mg/L and 465 mg/L, respectively (again, the semen level was below the
therapeutic concentration of 1000 mg/L).
•
80% of patients
taking nevirapine (Viramune)
exceeded the therapeutic blood concentration (> 3450 mg/L), and the mean semen
concentration was right about this level (3462 mg/L).
•
All participants
taking efavirenz (Sustiva) attained
therapeutic blood concentrations (at least 1000 mg/L), but no efavirenz penetrated
the semen.
The
investigators concluded that antiretroviral agents that suppress blood plasma
viral load also suppress seminal plasma viral load, despite differential drug
penetration of semen.
Based on these findings, they suggested that "Fully
suppressive antiretroviral therapy may reduce the risk of sexual transmission
of HIV-1."
This study adds to the evidence that HIV transmission is
likely to be rare if an HIV positive individual
is on effective antiretroviral
therapy, but does indicate the potential for a small residual risk.
8/29/08
Reference
D
Chan and J Ray. Differential penetration of antiretroviral agents in semen and
effect on seminal plasma HIV-1 RNA load. XVII International AIDS Conference (AIDS
2008). Mexico City. August 3-8, 2008. Abstract TUPE0077. |
