Taking Your Medicine: What To Do If You Miss A Dose Of PrEP

June 15, 2023

PrEP To Prevent HIV

Pre-exposure prophylaxis (PrEP) is a Food and Drug Administration (FDA) approved medication to help prevent human immunodeficiency virus (HIV) infection. People at high risk of contracting HIV benefit from the consistent use of this drug. Common examples include people with multiple sex partners, people who inject drugs (PWID), men who have sex with men (MSM), and serodiscordant couples. PrEP can be taken in pill form or given as a long-acting injectable. This medicine should be used as an additional protection measure alongside condoms and other prevention methods. To prevent contracting and spreading HIV, consistent use of PrEP is necessary.

How effective is PrEP?

The medication works by pre-loading the body with antibodies necessary to fight the virus. Should HIV enter the body, defenses are already in place to suppress viral load. If prescribed, PrEP can reduce the risk of acquiring HIV through sex by 99% or more. For people injecting drugs or sharing needles, PrEP has a more than 70% success rate. However, PrEP may be ineffective or unsafe if not taken as instructed.

What’s your dosage?

The recommended dosage of PrEP should be started at least 72 hours before a potential exposure to HIV to prevent infection. The first dose should be taken in the morning on an empty stomach. Typically, doctors prescribe 2 tablets of 10mg daily or 1 injection of 200mg weekly. Once initiated, the doses should be taken at the same time every day or week. PrEP can also be taken on-demand using the 2-1-1 strategy. The first dose of 2 pills is taken 2-24 hours before sex, the second dose 24 hours later, and a final pill 24 hours after the second dose. For continued PrEP use, the body takes several weeks to adjust to this medication. Treatment with PrEP can last for up to 3 years. However, treatment may need to be stopped if the person develops a health problem or if the medication starts to cause too many side effects.

When a missed dose happens

If a person misses a dose of PrEP, doctors recommend taking the pill as soon as possible. If the next dose is near, skip the missed dose and take the next dose at the usual time. Do not double up on the amount to make up for the pill missed. This may result in overdosing and causing unpleasant side effects. If a person misses a dose of the injection, see the doctor as soon as possible. After the makeup injection, return to the regular schedule. If the patient forgets the dose more than once, contact a doctor for further instructions. The doctor can recommend a few ways to adjust the protocol.

With PrEP, consistency matters

People at high risk of acquiring HIV should contact a local healthcare provider to see if PrEP can help. Once prescribed the medication, strictly follow all the instructions given by the doctor. If a dose is missed, take the pill as soon as possible. In case of any questions or doubts regarding the dosage or any side effects, talk to a doctor immediately to prevent complications and stay protected.


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