Cocaine and cannabis tests are typical examples of different bioassays of urine and hair that are not comparable, because they represent different time frames. By means of hair analysis, cocaine abuse is detectable for 2–6 months after a single 25–35 mg dose of drug administered intravenously[35]. A positive urine test can only be expected within 2–3 days after consumption of the drug. If one compares hair and urine assays for cocaine, it is reasonable to expect a lot of hair positive and urine negative results, considering the windows of detection for each assay.