HIV prophylaxis is divided into 2 categories: post-exposure prophylaxis (PEP) and pre-exposure prophylaxis (PrEP). PEP is the administration of antiretroviral therapy to an HIV negative person who may expose to HIV. Exposure can be occupational (oPEP) or non-occupational (nPEP), with non-occupational exposure being related to sexual or intravenous (IV) drug exposures. PrEP is the use of antiretroviral drugs in a high risk, HIV negative patient, to prevent future HIV infections.
Non-Occupational Post-Exposure Prophylaxis (nPEP)
Risk of HIV transmission after exposure is variable and linked to viral load, with higher viral load increases the risk of transmission. High viral loads can see in acute and early HIV infection. Co-infection with other sexual infections also increases the transmission of HIV infection. Although no prospective randomized clinical trial has been done to show the efficacy of PEP, some observational and case studies, along with expert opinion, have suggested that PEP might be useful in high-risk populations and it has led to widespread acceptance.
In 1997, Cardo and collaborators published a case-control study on HIV prevention. They showed an 81% reduction in HIV transmission in health care workers when they were given zidovudine after percutaneous exposure. Since then, many other clinical and observational studies have supported the use of PEP.
Risk of HIV transmission
The risk of HIV transmission differs and depends on the exposure route. It has done studies to estimate the per-act HIV transmission risk from an infected source to an HIV negative person. The estimated highest per-act risk for acquiring HIV through a blood transfusion is 9250 per 10,000. Receptive anal intercourse (138 per 10,000), needle sharing drug users (63 per 10,000), and percutaneous needle stick injuries (23 per 10,000) also had high levels of HIV transmission. Receptive penile-vaginal intercourse (8 per 10,000), insertive penile-vaginal intercourse (4 per 10,000) and oral sex (low) have much lower rates of transmission.
nPEP should start as soon as post-exposure has occurred for high-risk exposures and can start up to 72 hours after the event. It breaks exposure risks down into 3 categories: negligible, intermediate, and substantial.
HIV nPEP should only start in patients who are HIV-negative because a person presenting for nPEP treatment may already be HIV positive and unaware of his or her status. Baseline HIV testing should perform to all patients before starting nPEP. The CDC and NIH recommend the use of a rapid Ab or rapid Ag/Ab test. If early testing is not available, a non-rapid test should perform, and nPEP can be offered while results are pending.
When a patient is being tested for nPEP, one should also offer to test for other sexually transmitted diseases, including hepatitis B, hepatitis C, syphilis, gonorrhea, and chlamydia. A pregnancy test should get. Physicians should also test the renal and hepatic toxicity of antiretroviral medications a baseline creatinine, AST, and ALT.
It recommends follow-up labs at 4 to 6 weeks and should include a repeat HIV test, creatinine, AST, ALT, syphilis test, and pregnancy test. Repeat HIV testing should also occur three months after exposure to determine if HIV infection has occurred. Additional, it recommends testing at 6 months in patients with hepatitis C since this infection often has a delay in seroconversion.
Once starting with nPEP, the recommended protocol is a 28-day course of 3 medications. The preferred medication regimen for adults and adolescents aged older than 13 years, with normal renal function (creatinine clearance equal to 60 mL per min), including pregnant women, is tenofovir DF 300 mg and fixed-dose combination emtricitabine 200 mg (Truvada) once daily with raltegravir 400 mg twice daily or dolutegravir 50 mg once daily. Alternative regimens are available including regimens for patients with renal dysfunction and children 12 years and younger.
Adherence plays a vital role in effectiveness. Patients with suboptimal adherence have higher rates of failure. Studies comparing tenofovir-containing regimens with zidovudine-containing regimens have shown that patients given tenofovir-containing regimens do well. They can tolerate it, with fewer side effects and have higher completion rates.
It should provide additional treatment for other STDs, including hepatitis B, syphilis, gonorrhea, and chlamydia when the diagnosis confirms.
If nPEP fails, patients may develop signs and symptoms of acute HIV infection. Patients should know signs and symptoms of acute HIV infection and instructed to return if they become symptomatic. It usually associates acute HIV infection with a high viral load. Common symptoms include fever, fatigue, myalgia, and a skin rash. Less common symptoms include a headache, pharyngitis, cervical adenopathy, arthralgia, night sweats, and diarrhea.
Occupational Post-Exposure Prophylaxis (oPEP)
Risk of Transmission
The average risk of HIV transmission after occupational exposure is 0.3%. Risk varies depending on the exposure. It estimates the risk of percutaneous exposure at 0.23%, mucous membrane exposure at 0.09%, and cutaneous exposure at less than 0.09%. Several factors may associate with an increased risk of HIV transmission, including injuries from hollow-bore needles, visibly bloody devices, deep tissue injuries, and injuries during procedures involving a needle or device being positioned in an artery or vein.
oPEP should start as soon as possible, ideally within 2 hours. It should not delay initiation of oPEP while waiting for information or test results from the source patient. If oPEP started, and it is later determined the source patient to be negative, then oPEP can discontinue, and no further evaluation or treatment is necessary.
Source Patient Testing
It recommends HIV testing of the source patient whenever possible. Voluntary testing of the source patient is required, and laws on consent for testing differ by state. A rapid test is mandatory where available. If the source patient reports a high-risk exposure within the preceding six weeks, some guidelines (though not the CDC) recommend HIV RNA assay. HIV RNA can test the patient for infection during the "window period," which is the time frame between contracting the virus and developing an antibody response. However, there have been no documented cases of transmission during this window period. The source patient may test for hepatitis C (HCV) RNA and hepatitis B (HBV) surface antigen.
Baseline HIV testing of the exposed worker should get after an occupational exposure even if the exposed worker declines PEP. It can then perform repeat HIV testing at 4 weeks, 12 weeks, and 6 months post-exposure. Other baseline tests conducted on the patient at the time of initial presentation should include HCV antibody, and HBV if the individual has not vaccinated against hepatitis B.
It should also advise patients on avoiding donation of plasma, blood, tissue, or semen until confirmatory negative testing. Besides avoiding unprotected sex and pregnancy, and in breastfeeding women, the recommendation is stopping it, especially after high-risk exposures.
Pre-Exposure Prophylaxis (PrEP)
In 2015, about 1.1 million people age 13 and older in the United States were living with HIV. The number of new HIV diagnoses in the United States in 2015 was 38,500, which has declined since 2010. Although rates are falling overall, rates of new HIV diagnosis in specific subpopulations are not following this trend. Black men (especially males having sex with males-MSM) have shown no change, and rates among Hispanic MSM are increasing.
HIV seems to affect specific subsets of the population disproportionately. In 2015, 67% of newly diagnosed HIV cases were among MSM. 55% of new diagnoses were among adolescents and young adults (age 13 to 34), and 44% of new diagnoses were among blacks.
It developed prEP to help reduce the number of new HIV diagnoses. PrEP therapy includes tenofovir-emtricitabine, a single pill taken daily to prevent HIV infection. Multiple clinical studies have shown this regimen to be useful for PrEP. Overall, when taken as prescribed, it has found PrEP to be over 90% effective in preventing HIV infection. Based on that the FDA approved the use of tenofovir-emtricitabine for PrEP in 2012, and in 2014 PrEP clinical practice guidelines were developed by the CDC.
Physicians show PrEP in high-risk populations.
Heterosexually Active Men and Women
Men and Women Who Use Injectable Drugs
PrEP is indicated for only HIV-negative patients, and thus an initial HIV test should always be performed. A physician can examine the patients for signs and symptoms of acute HIV infection. Primary HIV infection symptoms include fever, fatigue, myalgia, rash, headache, pharyngitis, cervical lymphadenopathy, arthralgia, night sweats, and diarrhea. If signs of acute HIV are present and the initial HIV test is negative, the patient may still be infected with HIV but have no detectable HIV antibodies (the "window period"). Recommended evaluation for patients possibly in the window period includes HIV antigen/antibody test or checking viral load or rechecking HIV status in 1 month.
Renal function testing: Because tenofovir-emtricitabine can cause a decrease in renal function, it is recommended to get a baseline creatine clearance before starting PrEP.
Hepatitis B and hHepatitis C testing: Infection with hepatitis B or C viruses is not a contraindication for starting PrEP. Individuals who do not test positive for Hepatitis B should administer the HBV vaccination at the initiation of PrEP.
Pregnancy and STI: Pregnancy is not a contraindication for PrEP, but risks and benefits should be discussed with the patient, and an STI testing is done.
Tenofovir disoproxil fumarate (TDF) 300 mg plus emtricitabine (FTC) 200 mg. This regimen is available as a combination pill.
After starting PrEP, patients need to be followed every three months for repeating HIV and STI testing. It should test women for pregnancy. Besides, health care workers should educate patients about the signs and symptoms of acute HIV infection and medication side effects. A physician should also monitor renal function.
Risks include adverse reactions, the potential for selection of drug-resistant HIV, and the possibility of increased high-risk behavior by the patient.
Adverse reactions: The most common side effects of nPEP medications include fatigue, nausea, vomiting, headache, diarrhea, and other gastrointestinal (GI) complaints. These can often be treated with additional anti-emetic or anti-diarrheal medications. Severe reactions including nephrolithiasis and hepatitis have been occasionally reported.
Potential for selection for drug-resistant strains of HIV: This is another potential concern, but the frequency at which resistant strains develop is unknown. The potential risk can decrease by only prescribing nPEP to HIV-negative individuals and stressing the importance of adherence to treatment regimens.
The possibility of continuing or increasing high-risk behavior: High-risk behavior includes condom-less sex, multiple partners and insertive anal intercourse. Studies investigating this idea have shown mixed results. The majority showed no increase in high-risk behavior after receiving nPEP; however, a few studies showed nPEP users being more likely to have multiple partners or to engage in condom-less sex. Two of these studies showed that nPEP users were more likely to become HIV positive than patients who did not receive nPEP.
The emotional effects of an HIV exposure can be substantial, and proper follow up, and counseling can be beneficial to all patients. Prompt follow up provides an opportunity for patients to ask questions, ensures education, can increase compliance and can help the patient with managing side effects. Once antiretroviral therapy has started, the pharmacist should always monitor for adverse effects, which often lead to a drop in compliance.
It has been well established that an interprofessional approach to HIV-positive patients will increase adherence and allow for better outcomes. Expanding this interdisciplinary approach to encompass HIV prevention will help decrease HIV transmission rates and end the AIDS epidemic.
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