Gay and bisexual men taking PrEP before and after sex — known as the 2-1-1 regimen — reported good adherence and none were diagnosed with HIV, according to a new study from Kaiser Permanente San Francisco. Based on these findings, on-demand PrEP could be an attractive option for men who can plan ahead for sex.

"Some of our patients have been reluctant to take a daily medication, and enabling our patients to choose the dosing strategy that is right for them is very empowering," study co-author Dr. Jonathan Volk, of the Permanente Medical Group, said in a press release. "We now have different dosing strategies that can meet the needs of different patients."

PrEP 2-1-1 involves taking two doses of Truvada (tenofovir disoproxil fumarate/emtricitabine) between two and 24 hours before anticipated sex, one dose 24 hours after the initial double dose, and a final dose 24 hours after that.

A pair of French studies has shown that PrEP taken before and after sex is highly effective for men who have sex with men, regardless of whether they have sex frequently or less often. But so far, there has been little data from the United States.

Although the World Health Organization and the International Antiviral Society-USA have endorsed on-demand PrEP for gay and bi men, this regimen is not yet approved by the federal Food and Drug Administration. The 2-1-1 regimen has not yet been studied in women or transgender men who have vaginal or frontal sex. Study results for cisgender (non-trans) gay and bi men only apply to Truvada, not the Descovy (tenofovir alafenamide/emtricitabine) pill that was approved last year as a second daily PrEP option. Read more via Bay Area Reporter