What should you do if you’ve missed a dose of PrEP?

By Emen8, updated 4 weeks ago in Health / Sexual health

PrEP pills on yellow and blue background with circles focussing on missing a pill

It’s been a busy Monday and things haven’t gone to plan. You slept through your alarm, had to skip breakfast and barely made it to work on time. Things have been busy all morning and it’s only when you’re finally sitting down to have lunch that you realise you completely forgot to take your PrEP when you were supposed to.

So what happens now? You hooked up with a couple of guys over the weekend and didn’t use a condom, and you’ve missed your scheduled dose. Has your HIV protection been affected? What should you do now? How urgent is it?

Almost everyone who’s used PrEP has missed a dose at some stage. While 100 per cent adherence to any ongoing medication regime is rare, it’s not easy to know what to do – if anything – when you forget to take your pill.

To help clear things up, we spoke to Dr Edwina Wright, who is an HIV specialist at the Alfred Hospital and Central Clinical School at Monash University, and is Chair of the Australian PrEP Guidelines Committee at the Australasian Society of HIV, Viral Hepatitis and Sexual Health Medicine (ASHM).

What should you do if you’ve missed a dose of PrEP?

First of all, it depends on how you’re taking PrEP.

“The most common way that PrEP is used in Australia is in the form of daily PrEP,” says Dr Wright. “It involves taking one pill containing two antiviral drugs – tenofovir and emtricitabine – at the same time every day, and this provides highly effective protection from HIV.”

What happens if you miss a dose of daily PrEP?

“It’s important for people to know that having it a few hours late is not a big deal. For daily PrEP, it doesn’t have to be exactly 24 hours between doses,” explains Dr Wright. “If you realise you’re late taking your dose, just take the pill as soon as you can and then resume your regular PrEP routine the following day.”

And what if you miss a dose completely?

Also no cause for concern, says Dr Wright. “Missing a dose here or there won’t significantly impact the amount of protection you are getting. There’s no need to panic or double dose the next day. Just keep taking your normal dose at the normal time moving forward.”

It’s important to be aware that these guidelines apply only to cisgender men. For trans men, current research suggests that PrEP must be taken every day to maintain the necessary level of protection for vaginal or front-hole sex. If you have missed a dose of PrEP and had vaginal or front-hole sex without a condom, it’s best to inform your prescribing doctor as soon as possible. Make sure you keep taking one PrEP pill every day as this helps ensure your body stays protected — even after the event. Remember that it’s essential for trans guys to keep using daily PrEP for 28 days after condomless sex.

“… 100 per cent adherence to any ongoing medication regime is rare,”

What happens if you miss a dose of periodic PrEP?

The same principle applies for periodic PrEP, which is similar to daily PrEP, but over a finite period of time. Taking your pill at the same time every day is best, but you’re still protected if you’re out by a few hours, or if you accidentally miss a day.

But if you’ve missed a few doses in a row, you may not be maintaining high enough levels of PrEP in your body to protect you from HIV effectively. “If you’ve missed several days’ worth of PrEP and you’ve been having condomless anal sex with someone whose HIV status you don’t know, or someone who is HIV positive but doesn’t have an undetectable viral load you should go and speak to a doctor about starting a 28-day course of PEP,” says Dr Wright.

Again, if you’re a trans guy, missing even one dose of periodic PrEP may reduce your level of HIV protection. If you’ve missed a dose and had vaginal or front-hole sex without a condom, inform your doctor as soon as possible and be sure to continue taking one PrEP every day for at least 28 days.

It’s important to do this as quickly as possible. For PEP to be effective, it should be started within 72 hours of exposure to HIV, and ideally as soon as possible.

What about missing a dose of on-demand PrEP?

Things are a little bit different if you’re using on-demand PrEP. It’s important to take the initial double dose a minimum of two hours and a maximum of 24 hours before you have sex. Take the second dose 24 hours after the initial double dose (not 24 hours after you have sex), and then the third dose 24 hours after that.

“On-demand PrEP is effective for a short and specific period of time, and the follow-up doses can be tricky to time correctly,” Dr Wright says. “If you’re travelling or having a big weekend – which people may do when they’re using on-demand PrEP – it can be easy to forget to take them.”

Again, missing a follow-up dose by a couple of hours is nothing to worry about. But if you miss them altogether and you’ve had condomless anal sex during that time, go and see a doctor as soon as you can. This is also the case if you don’t wait a full two hours after the initial double dose before having sex.

“In this setting where a person has missed any of the doses of on-demand PrEP, a doctor or a specialist nurse practitioner will take a careful history to try and determine the risk that exposure to HIV has occurred. Based on your circumstances, you may well be offered a course of PEP.”

What if you’re missing doses of PrEP regularly?

If you find yourself missing doses frequently, it may be worth looking at why it’s happening. “People should recognise that their lives get busy and that they can’t always rely on themselves to remember every time.” says Dr Wright. “There are a lot of things you can use to help remind yourself when your next dose is due. Something as simple as setting an alert on your phone can be a big help.”

Easy tips to help you remember to take your meds! | Emen8

There are also a number of apps specifically designed for PrEP users, which contain detailed information about PrEP, along with scheduling help for all three regimes – one popular example is My PrEP (available for iOS or Android).

There’s no one-size-fits-all solution and people’s circumstances change – you may find that adhering to a PrEP regime isn’t something that works for you, for any number of reasons. “If you find that you are missing doses regularly, take some time for deeper reflection on why it’s happening, and whether the regime of PrEP you’re taking is the best choice for you,” says Dr Wright. “For example, if you’re not having much sex at all and you’re missing lots of doses of your daily PrEP, you could talk to your doctor about switching to on-demand PrEP. Or alternatively, if you frequently forget doses of on-demand PrEP and you’re having sex pretty often then maybe daily PrEP is a better choice for you. In the future, maybe injectable PrEP, which is given every eight weeks, will be the best choice for you.”

Importantly, don’t forget that PrEP is only one way to protect yourself from HIV. There are always other options when it comes to keeping yourself and your partners safe. PrEP, condoms, undetectable viral load, and PEP when it’s needed are all great options available in the HIV prevention toolkit.

How to get PEP in Australia

PEP is available in cities and regional areas, from selected emergency departments, sexual health services and doctors. Call in advance to make it clear that you want PEP. If it’s out of regular working hours, going to the emergency department might be your best option.

Some states and territories have PEP information phone lines you can call for information or to speak to the hospital on your behalf. Click on your state or territory for more on PEP where you’re based: ACT | NSW | NT | QLD | SA | TAS | VIC | WA

Exposed to HIV? Get PEP (Post-Exposure Prophylaxis) | Emen8