Drug abuse in various parts of the world is increasingly widespread. Therefore, a drug addict should immediately stop and must be recovered. To overcome the symptoms of addiction, the use of methadone as a synthetic drug to replace opioid type drugs is recommended. In this paper, an experiment with rehabilitation patients to identify the effect of the drugs on the brain activity in the frontal, central, temporal, and occipital lobes is proposed. The EEG data collection is performed using 18 channel electrodes, namely central: C3, C4; frontal: Fp1, Fp2, F3, F2, F4, F7, F8; occipital: P3, Pz, P4, O1, O2; and temporal: T3, T4, T5, T6. In the brain signals record, subjects were asked to comfortably sit in a chair. The recording was done in three sessions: 5 min before drinking methadone, 10 and 60 min after drinking the methadone, respectively. To reduce background noise and artifacts removal, bandpass filter (0.5–50 Hz) and wavelet method were applied, respectively. From this experiment, it was found that a decrease in amplitude after methadone intake for average in four lobes is obtained. The result indicates that the use of methadone is highly effected on the entire brainwave activity which indicates a decrease in the level of desire to do activities.