PEP is a course of medication that can usually prevent HIV from becoming established in the body. That way, you remain HIV-negative. PEP should be started as soon as possible following the risk of infection. You can find extensive information about PEP and the addresses of clinics which offer PEP here.
With other medical emergencies due to drug use, remember: intervening can save lives. If someone's life is in danger or if someone is unconscious, you should call emergency services ("Notruf," 112) immediately.
Self-help and drug advice centers also offer first-aid courses for drug users.