Have you heard of on-demand PrEP dosing?

There's a new way to PrEP!

The International Antiviral Society, the NYC Department of Mental Health and Hygiene, and the SF Department of Public Health (among many others) now endorses a second method of PrEP dosage.

When approved in 2012 for HIV prevention, FDA guidelines for PrEP called for taking the medication daily. While subsequent studies have shown that near daily adherence is effective, it wasn't until recently that a pilot study from the SF AIDS Foundation demonstrated that a higher dose initially, followed by a couple days of adherence was also effective.

On-demand PrEP dosage calls for the patient to take two pills 2 to 24 hours before sexual contact and continue taking a normal dosage as long as sexual activity persists, followed by one pill for the following two days after sexual contact has ended.

Sounds confusing, right? Don't worry, I've got a handy chart for you. It's actually REALLY simple!

The Science

Truvada is a combination of two medications that have been used in HIV treatment for decades: emtricitabine and tenofovir. Descovy is a similar medication, incorporating tenofovir alafenamide. These drug work by blocking a cellular enzyme called reverse transcriptase, which HIV uses to copy its genetic material and reproduce.

When a patient has enough of these medications in their blood stream, HIV is incapable of bonding to the patient's cells, rendering it incapable of reproducing. Fortunately, our bodies are inhospitable to HIV, so without the ability to reproduce, the virus quickly dies.

PrEP on-demand studies have shown is that two pills of Truvada or Descovy are enough to saturate the blood stream before potential contact with HIV. Continuing to take a normal dosage (1 pill) while sexually active keeps that saturation high enough, and maintaining that saturation for two days following sexual contact is long enough for the virus to die off.

Why is this so important?

Because daily adherence is hard, and having other effective dosage schedules allows more people to benefit from this medication. We can't predict what is going to come up in somebody's life, but we can give them the tools to meet those challenges successfully.

Why might a patient use on-demand PrEP dosing? Who knows?! Maybe they're headed to a sex party and want to take precaution, which is great. There are also many patients that struggle financially to get 12 refills a year. There are many people that have inconsistent work schedules that make daily adherence really hard.

At the end of the day, it's less important as to why somebody is taking PrEP a certain way, and more important to celebrate their healthy behaviors - both for themselves and their broader communities.

If you've got more questions about on-demand PrEP, please reach out!


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