Taking PEP after a risk exposure will not necessarily prevent infection.
HIV, like any virus, works by infecting some cells then replicating itself and spreading to other cells. There is evidence that it may take a few days from the time of exposure for HIV to establish itself in the body. The aim of PEP is to prevent HIV replicating itself in those first cells. The cells then die naturally within a short time, without having produced more copies of HIV.
The drugs used for PEP are the same anti-HIV drugs used to treat HIV and can create similar side effects to the ones experienced by positive people taking them – nausea, diarrhoea, headaches and tiredness.
PEP is most likely to be effective when taken immediately (within a few hours) after being exposed to HIV. The earlier he starts the treatment, the better. But it may still be effective taken up to 72 hours after the incident.
At the time of writing, PEP is only officially available in New South Wales, Australian Capital Territory, Queensland, Victoria and Western Australia . PEP is available on a limited basis in other parts of Australia.
The person exposed to HIV should seek medical advice as soon as possible. It is usually easiest to contact an HIV prescribing doctor or sexual health centre, but if these are not open at the time , Accident and Emergency at major hospitals should be able to help.
NSW residents can call a special PEP hotline for advice about where to get PEP: call 1800 PEP NOW (1800 737 669).