Our drug crime defense lawyers know that Nyquil can cause innocent individuals who are tested for drugs to show a false positive for methamphetamines. This is because those taking Nyquil can test positive for methamphetamines in the blood. Those who take Nyquil to treat their cold are at risk of being accused of taking methamphetamines. This is because Nyquil contains substances such as antihistamines (sedative substances) and hypnotics. As most of us who have taken the brand-name or generic version of Nyquil know, it’s a medication that should be taken at night because it can make you drowsy. Nyquil is an over-the-country medication that is used to subdue common cold symptoms.