Mychal Outlaw, Mercer University College of Pharmacy
According to the Centers for Disease Control and Prevention’s (CDC) Sexually Transmitted Disease Guidelines, herpes simplex virus type 2 (HSV-2) causes most cases of recurrent genital herpes. The CDC states that many cases of HSV-2 are undiagnosed due to the fact that many infected persons are asymptomatic and transmit the infection unaware of its existence. The Sexually Transmitted Disease Guidelines specifically mention the following study and the significance of pre-exposure prophylactic treatment with tenofovir for the prevention of HSV-2 and HIV transmission. All other suggested prevention methods by the CDC included non-pharmacological options1.
|Tenofovir Gel for the Prevention of Herpes Simplex Virus Type 2 Infection2|
|Design||Double-blind, placebo-controlled, randomized trial|
|Objective||To assess whether tenofovir gel prevents HIV infection in women|
|Study Groups||Four hundred twenty-nine eligible HSV-2 seronegative South African women were enrolled in the study and randomly assigned to receive either tenofovir gel or placebo gel; N= 429|
|Methods||The tenofovir group included 205 women while the placebo group included 224 women. The tenofovir gel and placebo gel had identical appearances and presentations. Subjects were instructed to insert one dose of the gel 12 hours before sex and a second dose as soon as possible after sex (preferably within 12 hours). No more than two doses were permitted in a 24-hour period. At each monthly study visit all used and unused applicators were recorded for assessment of adherence. Vaginal tenofovir concentrations were randomly measured for each participant in order to assess drug exposure.|
|Primary Outcome Measure||Positive testing for HSV-2 infection|
Results demonstrated that the use of tenovofir gel provided a 51% lower risk of HSV-2 acquisition for women when used in preventative treatment.
|Adverse Events||Common Adverse Events: N/A|
|Serious Adverse Events: N/A|
|Percentage that Discontinued due to Adverse Events: N/A|
|Study Author Conclusions||Women may use tenofovir gel in order to reduce the risk of acquiring sexually transmitted viral infections. Further data on the efficacy of tenofovir gel against HSV-2 acquisition are needed.|
This study was not originally designed to assess the effectiveness of tenofovir for preventing HSV-2 infections in women. Tenofovir concentrations at the time of HSV-2 acquisition could not be assessed. Therefore, adherence to the treatment cannot be verified, and poor adherence could be explored as a variable for acquiring the infection. Although the tenofovir concentration for each woman was randomly checked, it cannot be assumed that the concentration at that particular time reflected the concentration of drug present during an exposure to HSV-2.
This study shows that tenofovir gel may be an effective option for reducing the risk HSV-2 transmission for women during sexual intercourse. The effectiveness of tenofovir gel was dependent on the adherence of the subjects to the study protocol. If the use of tenofovir was done according to the study protocol, vaginal delivery of the drug would equal to or exceed a concentration of 10,000 ng per milliliter. At this concentration, tenofovir offers a 63% higher rate of protection against HSV-2 compared to women without tenofovir treatment2.
- Centers for Disease Control and Prevention. Sexually Transmitted Diseases Treatment Guidelines. MMWR 2010;59(No. RR-12):20.
- Abdool karim SS, Abdool karim Q, Kharsany AB, et al. Tenofovir Gel for the Prevention of Herpes Simplex Virus Type 2 Infection. N Engl J Med. 2015;373(6):530-9.