HIV blocking drugs have a success rate of over 99% within 72 hours, and the earlier they are taken the better the results. HIV blocking drugs are mainly used for prophylaxis after high-risk exposure to HIV, and are commonly used such as tenofovir and emtricitabine. These blocking medications are best taken within 2 hours of exposure and are generally recommended to be taken no longer than 24 hours. It has been found that it takes 72 hours for HIV to spread from the localized area of infection, and it is also possible to prevent HIV replication within 72 hours of high-risk sexual exposure. Therefore, it is recommended to take HIV blocking drugs as soon as possible after high-risk sexual contact, and at the same time need to be taken continuously for 28 days without interruption. And pay attention to regular review to monitor the situation of blockade. It is recommended to consult a medical professional for standardized diagnosis and treatment if necessary.