One of the strategies for preventing HIV transmission is the provision of HIV Pre-Exposure Prophylaxis (PrEP). For HIV-negative patients with high-risk behaviors, PrEP using antiretroviral drugs is a proven way to prevent new HIV infections.

The data shows that approximately two million new infections of the human immunodeficiency virus (HIV) occur annually throughout the world. Because of the unavailability of effective vaccines to prevent HIV transmission, prevention strategies are needed for this. One of preventing HIV transmission strategies is the provision of HIV Pre-Exposure Prophylaxis (PrEP). For HIV-negative patients with high-risk behaviors, PrEP using antiretroviral drugs is a proven way to prevent new HIV infections.

HIV Pre-Exposure Prophylaxis


Before deciding to initiate HIV PrEP, clinicians should conduct several evaluations. These evaluations include a substantial risk assessment of HIV acquisition, evaluation of clinical eligibility for PrEP initiation, PrEP initiation regimens, monitoring, and termination of PrEP.

Substantial Risk Assessment of HIV Transmission

The initial step before initiating HIV PrEP is to carry out the risk assessment of HIV transmission. The main populations at high risk for HIV transmission include men who have sex with men (MSM), sexually active heterosexual women and men, injecting drug users, commercial sex workers, transgender (men/women), and prisoners. 

The substantial risks that further increase the likelihood of HIV transmission in the population are inconsistent behavior or not using condoms during anal or vaginal intercourse, sex partners who are HIV positive (serodiscordant couple), people who frequently change sex partners, HIV positive injecting partners, sharing injection equipment, and recent bacterial sexually transmitted infections (STI) such as gonorrhea, chlamydia, or syphilis. All populations above who have a substantial risk for HIV transmission are recommended to get PrEP.


Evaluation of Clinical Eligibility Before HIV PrEP Initiation

Clinical eligibility evaluation before the initiation of PrEP involves checking the patient's HIV status by conducting a rapid anti-HIV antibody test or HIV RNA test in patients suspected of having HIV with acute symptoms or who have a high risk of exposure to HIV transmission within the previous 4 weeks. Also, assessing kidney function, hepatitis B profile, hepatitis C, osteoporosis, and pregnancy risks were assessed. Absolute contraindications to PrEP administration are patients with HIV positive infection.

Assessment of Renal function, hepatitis B and C profiles, risks of osteoporosis, and pregnancy are needed to consider the benefit-risk ratio of tenofovir use in the PrEP regimen. Patients who have hepatitis B or C infection, impaired kidney function, high risk of osteoporosis, or pregnant need to be counseled with relevant specialists before continuing on PrEP (case-by-case basis). The estimated glomerular filtration rate should be above 60 mL/min / 1.73m2 before the tenofovir administration.

The assessment of patient compliance with the PrEP regimen is still needed. Things assessed are those that affect compliance, such as depression, stigma, or using illegal drugs. These things need to be addressed by involving the patient or the patient's family. If not handled properly, these things can reduce patient compliance so that the efficacy of PrEP will not be achieved.


PrEP Initiation Regimen According to Clinical Guidelines

At present, there are two main recommendations in the management of PrEP, according to the Central Disease Control (CDC) in the United States and the British HIV Association (BHIVA) / British Association for Sexual Health and HIV (BASHH) in the UK.

The latest CDC guidelines in 2010 recommend daily PrEP with a fixed-dose combination of tenofovir disoproxil fumarate (TDF) 300 mg and 200 mg oral emtricitabine (FTC) once a day for MSM populations, male/female heterosexuals, injecting drug users with substantial risk for HIV transmission and for patients whose HIV-positive partners (HIV-serodiscordant couples). PrEP in adolescents is not recommended because there is still a lack of evidence supporting both efficacy and safety. Coepally-timed or on-demand / non-continuous daily use is not recommended. There are no differences in the administration of PrEP regimens in MSM populations / heterosexual individuals or injecting drug users.

Whereas the 2019 BHIVA / BASHH guidelines recommend PrEP with a combination of TDF 300 mg - FTC 200 mg once daily or on-demand to MSM subjects with the substantial risk of HIV transmission, heterosexual men and women, transgender, and HIV-negative MSM in young ages ( 15-25 years).

A single dose of tenofovir can be given to male / female heterosexuals if they have contraindications to FTC. The method of administering PrEP on-demand includes an initial dose of two TDF-ETC combination tablets taken 2 - 24 hours before coitus, followed by a third single dose tablet, 24 hours, and a fourth single dose tablet 48 hours later. 

The PrEP on-demand regimen is not recommended for individuals with chronic hepatitis B infection. The current guidelines do not provide a specific duration regarding the provision of PrEP. As long as the patient lives a substantial risk of HIV transmission, PrEP should continue.

There is no fundamental difference in the PrEP regimen recommendations of the CDC or BHIVA/ BASHH in each population at substantial risk of HIV transmission, except in the case of adolescents. Both guidelines emphasize that the regimen for giving PrEP in special cases such as patients infected with hepatitis B/C, pregnancy, or kidney failure is decided on a case-by-case basis after consulting from relevant specialists based on risk and benefit considerations. For these specific cases, there are no recommendations for alternative regimens other than tenofovir and emtricitabine for PrEP. Multicenter studies are currently underway comparing alternative alafenamide tenofovir regimens.

PrEP monitoring

Both the CDC guidelines and BHIVA/BASHH recommend that PrEP monitoring be carried out regularly every 3 months. The steps at this stage are the examination of HIV (HIV antigen or antibody test), assessment of acute HIV symptoms, assessment compliance regimen, the examination of drug side effects (renal function test, osteoporosis risk assessment with DEXA scan / FRAX tool), tests pregnancy, and examination of sexually transmitted infections.


Recommendations for Termination of PrEP

The CDC and BHIVA/BASHH guidelines recommend stopping PrEP if the patient is concerned with HIV positive. Hepatitis B/C infection, suboptimal adherence, renal insufficiency are contraindicated.

References
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2. Delgado A. pre-exposure HIV prophylaxis. Medscape [Online]. Available from URL: https://emedicine.medscape.com/article/2054869-overview
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9. Centers for Disease Control and Prevention (CDC). Preexposure Prophylaxis Fort The Prevention of HIV Infection In The United States-2017 Update. Internet [Online]. Available from URL: https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2017.pdf
7. British HIV Association. BHIVA/BASHH guidelines on the use of HIV preexposure prophylaxis (PrEP) 2018. HIV Medicine (2019), 20 (Suppl. S2), s2--s80. DOI: 10.1111/hiv.12718


Source
1. https://www.alomedika.com, written by dr. Eduward T (internist)
2. Picture: https://www.dailymail.co.uk/health/article-4125530/HIV-treatment-makes-patients-susceptible-syphilis.html