A case of PEP failure

Posted on January 14, 2013 by drtan

Update 22nd July 2014

Since last year, we have switched to using a different PEP regiment in line with the latest recommendations by WHO and US CDC.

These new medicines have much fewer side effects and are more effective in preventing HIV.

Since switching to the new medicines, we have yet to see any cases of PEP failure.

Click here to learn more about PEP Treatment at our Clinics



Click here to learn more about HIV/STD Screening and Treatment services at our Clinics.






Original Article published in Jan 2013:


I hate PEP failures. It is probably one of the worst things a patient has to go through. After spending all that money and enduring 4 weeks of medicines with horrible side effects only to find out that the medicines did not work and to top it all off facing the prospect of living with HIV for the rest of his life is almost too much for most patients to bear.

I’ve fortunately had a good run. All my PEP failures have been either patients who started PEP after the recommended 72 hours treatment window, or who did not complete their treatment. So the failures were in some way or another ‘expected’. But as they say, all good things must come to an end.

A few weeks ago, I met a patient whom we will call Mr. M. Now Mr. M fits to a T, the most typical profile of a patient consulting for HIV related issues. He is a Chinese Singaporean, in his 30’s and works in a white collar managerial position in a large MNC. As with most of his peers, he occasionally indulges in commercial sex.

On that fateful evening, he was out with a group of friends and they all decided to visit Singapore’s notorious red light district known as Geylang. There, he met a Vietnamese lady plying the streets looking for work, a so called ‘street walker’. After the deal was struck, he made his way with her to a room.

What makes the story all the more tragic is Mr. M actually did everything right. He used a condom, he did not have anal sex and he only had vaginal sex. The only sad twist in the tale is that his condom broke.

Mr. M came to see me all ashen faced exactly 34 hours post exposure. We had a long talk about his exposures risks and the pros and cons of starting PEP treatment. A baseline HIV test was negative. We decided to proceed with the standard PEP protocol.

Mr. M took to the PEP very well. He had very limited side effects. Of course, over the next few weeks, Mr. M was understandably nervous as most people on PEP would be. He visited me several times for a variety of symptoms.

Within the first week of commencing PEP, Mr. M saw me for an irritated throat and some phlegm in the throat. I reassured him that it was too early for ARS symptoms.

During the second to third week, he saw me for constipation and red spots on his body that I diagnosed as Campbell de Morgan spots which are again not related to HIV. As for the constipation, we figured that it was due to his loss of appetite secondary to the PEP medications.

Towards the end of his PEP course, Mr. M was actually feeling much better. His throat no longer felt irritated, he never had a fever, he never had a rash and he never had diarrhea.

So on his first follow up visit, both of us were relatively confident of the outcome of the HIV test. Therefore, we were both completely blind-sided by what happened next.

As with all other PEP patients, I drew his blood for various tests and took one drop of it to run the Determine rapid HIV ½ test. We were chatting casually while the rapid test was running. The minutes ticked by and the test was looking better and better. However, at about the 10 minute mark, I noticed a faint line appearing in the patient window. This is not an uncommon thing to happen and is sometimes just due to the reagent slowing down as it passes the test area. However, Mr. M’s was different. As the clock ticked to 15 minutes passed, the patient line became more and more obvious albeit still relatively faint. At 20 minutes, the patient line was still faint but unmistakably present.

We proceeded to a Western Blot test and after 2 grueling weeks of waiting, the Western Blot came back as frustratingly ‘Indeterminate’. We discussed carefully the next steps. We could have decided on an RNA PCR viral load test which would cost more or repeat an ELISA and Western Blot test. We finally decided on the latter. This time round, the results were unambiguous: HIV ELISA – Reactive, HIV Western Blot Confirmation test – Positive.

Mr. M was devastated, inconsolable. My words of consolation rang hollow even to my own ears. He now has to walk down a very long road of living with HIV.

Learning points:

1. PEP is NOT 100% effective. The limited studies on PEP efficacy reports success rates of between 80% and 87%. Please do not think PEP is your ‘get out of jail card’. The ONLY way to be sure you do not catch HIV is to either abstain from sex or have only 1 mutually monogamous partner.

2. Always attend your follow up. Doctors ask you to go back to visit them for a good reason.

3. Do not rely on symptoms to diagnose or exclude HIV.