Pre-exposure prophylaxis (PrEP) is a medication regimen for HIV-negative individuals to reduce their risk of acquiring HIV. It works by blocking the virus from establishing an infection. For PrEP to be effective, it must be taken consistently as prescribed.
Understanding PrEP Protection
PrEP works by maintaining consistent levels of antiretroviral drugs in the bloodstream. The medication, typically a combination of tenofovir and emtricitabine, targets an enzyme HIV needs to replicate, preventing the virus from taking hold if exposure occurs. These drugs must build up in the body to reach protective concentrations.
For daily oral PrEP, it takes about seven days of consistent use to achieve maximum protection for receptive anal sex. For receptive vaginal sex or exposure through injection drug use, this protective level may take up to 21 days of daily use to develop. Missed doses can decrease drug levels, reducing PrEP’s ability to prevent HIV infection.
Addressing Missed Daily Doses
If you are on a daily PrEP regimen and miss a single dose, take it as soon as you remember, provided it’s within 12 hours of your usual dosing time. If more than 12 hours have passed, skip the missed dose and take your next scheduled dose at the usual time. Do not take a double dose to compensate, as this offers no additional benefit and can increase side effects.
Missing one or two pills occasionally on a daily regimen does not significantly reduce PrEP’s effectiveness, especially if you have been taking it consistently for a while. If you miss multiple doses, particularly more than two in a week, or if you stop taking PrEP for a week or more, your protection may be reduced. You might need to re-establish consistent dosing for a period, such as seven days, before full protection is restored.
Addressing Missed Event-Driven Doses
Event-driven PrEP, also known as PrEP on demand or the “2-1-1” method, involves taking a specific sequence of pills around sexual activity. This means taking two pills 2 to 24 hours before sex, followed by one pill 24 hours after the initial dose, and another pill 24 hours after the second dose. This method is primarily recommended for individuals engaging in anal sex.
If you miss a dose within the event-driven regimen, your protection could be significantly reduced. If you are late with the pre-sex dose, taking the double dose as soon as possible can still offer some protection. If you forget a post-sex dose, take it as soon as you remember. If more than 12 hours have passed since a post-sex dose, its effectiveness may be compromised, requiring additional caution. Strict adherence to the 2-1-1 protocol is important for its effectiveness.
When to Contact Your Provider
Contact your healthcare provider if you have missed multiple PrEP doses, or if you have concerns about potential HIV exposure after missing doses. They can assess your individual risk and discuss whether post-exposure prophylaxis (PEP) might be an option, which must be started within 72 hours of a possible exposure.
Consult your provider if you are unsure how to proceed after a missed dose, experience side effects, or are consistently missing doses. Your healthcare professional can offer personalized advice, help you restart PrEP correctly, and conduct necessary testing.
Strategies for Consistent Dosing
Consistent PrEP dosing is crucial for its effectiveness. Incorporating strategies into your daily routine can help prevent missed doses. Setting alarms or reminders on your phone or using pill reminder apps are helpful. Integrating PrEP intake with an existing daily habit, such as brushing your teeth or having breakfast, can improve adherence.
Using a pillbox helps track daily doses. Keeping your medication in a visible and accessible location also serves as a reminder. If you struggle with adherence, communicate openly with your healthcare provider. They can discuss challenges and explore alternative strategies or dosing options.