The drowsy effect experienced after taking NyQuil primarily stems from the inclusion of antihistamines in its formulation. These medications, designed to alleviate allergy symptoms such as runny nose and sneezing, also possess sedative properties that induce sleepiness. The presence of doxylamine succinate or diphenhydramine, common antihistamines in NyQuil, directly contributes to this outcome.
Understanding the mechanism behind this side effect is crucial for safe and effective medication use. While the sedative properties offer relief for nighttime cold and flu symptoms by promoting rest, they can also impair cognitive function and coordination. Historically, antihistamines have been recognized for their dual role in both allergy treatment and sedation, influencing the development and application of various over-the-counter remedies.
