Pre-exposure prophylaxis, commonly known as PrEP, is a medication taken by HIV-negative individuals to prevent HIV infection. This article explains the significant health implications of taking PrEP while HIV positive, emphasizing why knowing one’s HIV status before and during PrEP use is important.
How PrEP Works
PrEP utilizes antiretroviral drugs, specifically combinations like tenofovir disoproxil fumarate and emtricitabine (Truvada) or tenofovir alafenamide and emtricitabine (Descovy). These medications work by blocking HIV from establishing an infection within the body if exposure occurs. The drugs interfere with the virus’s ability to replicate. PrEP is intended for prevention in HIV-negative individuals, a different purpose from antiretroviral therapy (ART), which is the treatment regimen for people already living with HIV. The dosages of the drugs in PrEP are lower than those used in full HIV treatment, designed to prevent infection rather than suppress an existing one.
Developing Drug Resistance
Taking PrEP when already HIV positive, even unknowingly, exposes the existing virus to a suboptimal dose of antiretroviral drugs. This partial exposure creates an environment where the HIV can mutate, leading to drug resistance. The virus becomes less susceptible to PrEP drugs like tenofovir and emtricitabine. Drug resistance can develop if an individual has an undetected HIV infection when starting PrEP, or if they acquire HIV while using PrEP and it remains undiagnosed.
The risk of HIV drug resistance is highest when oral PrEP is initiated during acute, undiagnosed HIV infection. During this early phase of infection, the virus is rapidly replicating, and exposure to only a few antiretroviral drugs, rather than a full combination, can lead to the selection of resistant viral strains. These resistant strains then multiply, making the particular drugs ineffective for future HIV treatment.
Consequences for Future Treatment
If drug resistance develops due to PrEP use while HIV positive, it directly impacts an individual’s long-term HIV management. Resistance to drugs like tenofovir and emtricitabine means these specific medications, and potentially others in the same drug class, will be ineffective as part of a comprehensive HIV treatment regimen. This limits the available options for effective antiretroviral therapy (ART).
Individuals may then require more complex, potentially more expensive, or less tolerable drug combinations to achieve viral suppression. Effective ART is important for managing HIV, maintaining the health of the individual, and preventing onward transmission of the virus. Drug resistance complicates this process, making it harder to find an optimal and sustainable treatment plan.
The Critical Role of Testing
Given the risks, it is important to be tested for HIV before starting PrEP to confirm an HIV-negative status. This initial test helps prevent the development of drug resistance in individuals who might unknowingly be HIV positive. Regular HIV testing is also important while on PrEP, typically recommended every three months for oral PrEP users, to quickly detect any new infection.
If an individual tests positive for HIV while taking PrEP, they must immediately consult a healthcare provider. This allows for a prompt transition to a full HIV treatment regimen (ART) tailored to their specific viral strain and resistance profile, preserving future treatment options. Regular testing ensures that HIV infection, if acquired, is managed effectively without compromising future treatment success.