You wake up with a feeling of dread in the pit of your stomach. The condom broke, you regret agreeing to unprotected sex or you’ve heard from the rumour mill that a bareback sex partner is HIV-positive. Post-exposure prophylaxis (PEP) is a drug therapy that can prevent HIV from establishing itself in newly exposed people. You take a course of medication for a month after suspected exposure and it greatly reduces the chances that you will become HIV positive.

On the face of it PEP can seem like an easy rewind to a potentially life-altering mistake; a pharmaceutical get-out-of-jail-free card.

“I don’t think it’s widely known that this option exists,” says Rui Pires, education and training coordinator for the AIDS Committee of Toronto (ACT). “When people find out, there are many questions about how it works.”

First approved for use in Canada in 1996 for healthcare workers who may be exposed to HIV on the job, PEP is a combination of antiretroviral drugs. Though HIV may be present in a person’s blood immediately after exposure, it takes time for the virus to entrench itself in the body. Taking the drugs during that window of opportunity can stop the virus from taking hold, explains Darrell Tan, a clinical associate at Toronto General Hospital’s Immunodeficiency Clinic.

“If an appropriate regimen is started the chances of preventing HIV from infecting immune cells is very, very good,” says Tan. “But it’s not perfect.”

It isn’t a cure for HIV or a replacement for safer sex practices, says Tan. The treatment only works for a brief period after exposure. Its effectiveness decreases quickly over time.

“Even hours can make a difference,” Tan stresses.

According to World Health Organization guidelines, PEP should ideally be started within 24 hours of suspected exposure. After 72 hours PEP loses its effectiveness almost completely.



In Canada the typical length of PEP treatment is 28 days. When taken properly PEP drugs can reduce the risk of HIV transmission by 80 to 90 percent, according to information compiled by the Canadian AIDS Treatment Information Exchange. But skipping doses or prematurely stopping the treatment can drastically increase the chances of contracting HIV.

That last point is important, says Tan, because otherwise healthy people using PEP tend to report the most severe side effects, such as nausea and upset stomach.

ACT director of programs and services Le-Ann Dolan took PEP after receiving a needle stick injury in 2004. She says her reaction to the medication was so bad she quit taking the drugs after five days.

“It knocked me out,” says Dolan. “I couldn’t get out of bed…. I felt like I was being poisoned.”

Tan encourages those considering PEP to “work with their physician to find a PEP regimen that doesn’t cause intolerable side effects.

The cost of PEP is covered under workplace insurance for medical personnel and by the province for sexual assault victims. But it isn’t covered under the Ontario Health Insurance Plan for those who think they became exposed during consensual sex. A month’s treatment can cost between $1,000 and $1,500 depending on the drugs prescribed, Tan estimates.

Jane Greer, an administrator for Toronto’s Hassle Free Clinic, says she’s seen patients who have sought referral for PEP after engaging in risky sex only to change their minds after learning how much the treatment will cost.

It is a scenario in which it’s cheaper for a patient to risk becoming HIV positive than it is to stop a suspected infection before it even starts. It also means that PEP is simply inaccessible to those who can’t afford it.

“It’s a huge barrier for some people,” says Greer. “I see [PEP] very much as a medicine that should be available to those who need it.”

The Hassle Free Clinic refers those who seem like good candidates for PEP to St Michael’s Hospital, which is equipped to provide follow-up care including counselling, blood work and monitoring for adverse reactions to the medication.

But even ACT doesn’t know for sure which hospitals offer PEP for non-occupational exposure to HIV, Pires says, though that the information gap is gradually closing.

In April ACT completed a survey of nine Toronto-area emergency rooms and urgent care clinics. Of the nine hospitals, seven — Sunnybrook and Women’s College Health Sciences Centre, St Michael’s, Toronto General, Toronto East General, Toronto Western, Mount Sinai and the Centre for Addiction and Mental Health on College St — said they offer prescriptions for PEP or ready-made PEP starter kits.

Only St Joseph’s Hospital, an affiliate of St Michael’s, and the Hospital for Sick Children say they don’t offer PEP in their emergency care centres, Pires says.

Some worry that the availability of PEP could hamper prevention efforts. If you can just take some morning-after pills, why worry about safer sex? But if Dolan’s experiences are any indication, the meds can also serve as a potent reminder for people to take precautions to avoid exposure to HIV. 

“The treatment caused me to evaluate some of my decisions around sex… because I would do just about anything to avoid going on [PEP] again,” she stresses.