The cases in which the application of blocking drugs is not recommended are usually for the transmission of AIDS. The doctor does not recommend the application of blocking drugs, most likely because he or she judges that the risk of transmission of HIV from the corresponding behavior is extremely low, close to 0%. For example, in the case of sex with a stranger, where protective measures are taken throughout and there is no exchange of fluids from the genital tract, doctors generally do not recommend the application of interceptive drugs because the possibility of transmission is already very low indeed. Another situation in which blocking drugs are not recommended is when there has been an incident of HIV transmission for a long time, significantly more than 72 hours, so the application of blocking drugs at this time is not too effective, so the application of blocking drugs may not be recommended at this time. However, whether or not to apply it is merely recommended by the doctor, and should also depend on one’s own judgment. If you choose to apply the blocking drug yourself, you need to stick to it for 28 days without any interruption in between.