In some clinics, treatment of heroin addiction under an anesthetic is still used and consists of two phases. During phase one, the addict is anesthetized and given Naltrexone, which immediately blocks the effects of heroin. The user experiences some serious withdrawal symptoms but is not aware of them because of the anesthetic. During phase two, the user keeps on using Naltrexone for the next ten months to prevent relapse into the old habit, since Naltrexone blocks the effects of heroin. So taking heroin is useless. After a long period of using Naltrexone, the need for heroin will decrease. Besides using the medication, treatment takes place in a health care center, for instance by having talks with therapists. However, research on this treatment is still being done.