✅510(K) Cleared and CLIA Waived for OTC use; sensitive 200 ng/ml cutoff. Positive Results & the Detection Window (1) Cotinine may stay in the system longer for heavy and regular smokers who have a slower metabolic rate or whose kidney does not clean the nicotine out at a steady rate. (2) Smoke replacement therapy like Nicotine Gum, Nicotine Patch, and Nasal Spray that contain nicotine as well can elongate the positive detection time