HIV blocking drugs are drugs that are normally used to fight against HIV. They are taken early after a high-risk behavior or occupational exposure because the body may be infected with HIV, so taking these blocking drugs early before the virus only replicates locally and does not replicate in large numbers to infect other cells can inhibit the replication of the virus to the greatest extent and remove the virus from the body to stop HIV carriage. Generally, the earlier the blocking drugs are used, the better, and the success rate of blocking can be more than 99.5% when taken within 2 hours. If taken within 2 hours, the blocking success rate can be more than 99.5%. The latest is not more than 72 hours, and the blocking effect decreases if taken more than 72 hours. The general blocking drug is a combination of three drugs, the course of treatment for 28 days, in between can not be interrupted.