What is post exposure prophylaxis or PEP?
Post exposure prophylaxis (PEP) is the method of taking anti retro viral medications after a potential exposure to the HIV to prevent being infected with HIV. It is taken in an emergency situation and needs to be taken within 72 hours of potential exposure. Should be used only in emergency situations and is not ideal for people potentially exposed to HIV frequently.
There are two types of post exposure prophylaxis. One that happens when a STD Specialist takes PEP who has a possible exposure during his/her work routine most commonly by needle stick injury( occupational post exposure prophylaxis ) and the other (non occupational post exposure prophylaxis) is when they take PEP for an exposure not related to their occupation like sexual intercourse or during drug use.
When to take PEP?
PEP is taken once or twice a day for 28 days. It is not a substitute for pre-exposure prophylactic methods such as using condoms, sterile needles, universal precautions and taking pre-exposure prophylactic medicines. The individual must continue taking precautionary measures while taking PEP.
The people prone to potential contact with the HIV virus are:
- Those having unprotected sexual intercourse
- People with multiple sexual partners
- By Shared needles
- Anal intercourse
- Health care professionals
- Sexual assault victims
The risk factors for post exposure development of HIV infection in certain common situations are as follows:
1) 4 per 10000 exposures for sexual intercourse with an infected individual
2) 138 per 10000 exposures for anal intercourse with an infected individual
3) 23 per 10000 exposures for per-cutaneous needle stick injuries (0.3%)
4) Cutaneous contact: the risk with cutaneous contact(non intact skin) with a HIV positive individual is 0.09%
5) Mucous membrane contact: This is also 0.09%. The risk however is larger if the source has a higher viral load and a larger volume exposure.
PEP Treatment Procedure:
Assessment: This is the initial step in the path of initiating PEP.
Immediate cleaning of the area with antiseptic if not already done by the health care professional.
- Clinical assessment is done to assess the mechanism of exposure.
- Eligibility of the patient is assessed. Criteria such as whether the exposure is within 72 hours, the HIV status of the source if possible, parenteral or mucous membrane exposure and exchange or exposure to body fluids such as blood, blood stained saliva, breast milk, genital secretions, CSF, amniotic , rectal, peritoneal, synovial, pericardial and pleural effusions.
- HIV testing of the source and exposed individual is done if possible. This however should not delay the initiation of treatment. If the source status is not known then they can be voluntarily tested for HIV, HbSAg and HCV status.
- Baseline investigations such as complete blood count (CBC), renal function tests and alanine transaminase( ALT ) are done prior to initiation of treatment.
- Non eligible: if the exposed is already HIV positive, if the source is already established as HIV negative or contact with body fluids without significant risk such as tears, non blood stained saliva, urine and sweat.
Counselling and support:
The next important step in the care of patients with exposure history is to counsel these patients regarding:
- Risk of acquiring HIV infection with their exposure
- Risks/side effects associated with PEP and the benefits/ need for its initiation.
- Counselling for the patient to adhere to the entire course of PEP
- Informed consent is obtained as post exposure prophylaxis is not mandatory.
- Special counselling in case of sexual assault.
Prescription of drugs for Post Exposure Prophylaxis:
Drugs to be taken for post exposure prophylaxis are readily available and needs to be taken as soon as possible within 72 hours. It has the best efficacy if started within 2 hours of exposure. It’s a 28 day anti retro viral therapy and needs to be age appropriate. Care needs to be also taken to keep in mind any underlying co morbidities and drug interactions. There should never be a delay in treatment due to consideration of the correct regime for treatment.
A 2 / 3 drug regime is initiated but a 3 drug regime is preferred. It is given as a once daily or twice daily dosage depending on the drug prescribed. Anti retro viral agents like tenofavir (TDF) and lamivudine (3TC)/ Emtricitabine (FTC) can be started for adults and adolescents and use lopinavir(LPV) /ritonavir (r) / atazanavir(ATV) as the third drug in the regime. TDF +3TC (or FTC) is preferred as there is a strong recommendation from multiple studies that there is better consistency among patients who are prescribed to these drugs.
The third drug alternative of LPV/r/ATV is used as it is widely available in low and middle income countries as well and has proven to be effective. Another drug that can be used is Efavirenz but its use is limited as it is not tolerated well in HIV negative individuals. The choice of anti retro viral drugs is up to the doctor treating you based on your assessment. It is important to take the drugs prescribed in the right way and the right time everyday to ensure maximum effectiveness.
PEP can also be given during pregnancy during any of the semesters after significant exposure to HIV as evidenced in multiple trials avoiding only certain drugs such as efavirenz ( in the first trimester) and indinavir (pre natal) which are not suitable.
All HIV exposed children must receive co-trimoxazole prophylaxis from 4 to 6 weeks of age. It is given in the dosage of 5mg /kg body weight every day as a single dose until the HIV status of the child is confirmed.
The side effects of anti retro viral drugs are minimal. The most common side effects are:
- Nausea and vomiting: these are minimal and can be managed easily. Drugs should not be discontinued on account of this.
- Headache, fatigue and insomnia are also sometimes seen.
- Anaemia, leucopenia and thrombocytopenia may also occur.
- Hepatic flares: this is a side effect seen in patients who are HbSAg ( hepatitis B ) positive. Hepatic flares can occur in patients once some drugs such as lamivudine or emtricitabine are stopped and hence the HBV status of these patients needs to be monitored carefully once the drugs are stopped.
Effectiveness of PEP Treatment:
PEP is extremely effective when taken correctly but is not 100% effective. The sooner you start PEP after the possible exposure the better it is.
All individuals who have high risk behaviour or at a high risk of contracting HIV infection or those who report more than 1 time usage of non occupational PEP should be advised on risk reduction measures and considered for pre exposure prophylaxis(PrEP).