NyQuil's active ingredients—acetaminophen, dextromethorphan, and doxylamine—have different half-lives, which affect how long NyQuil stays in your system:
- Acetaminophen has a half-life of about 2 to 3 hours and generally clears from the body within 4 to 6 hours.
- Dextromethorphan has a half-life ranging from 3 to 6 hours, remaining in the system for about 6 to 12 hours.
- Doxylamine , an antihistamine causing drowsiness, has a longer half-life of approximately 6 to 12 hours, potentially staying in the body up to 24 hours or more
Overall, NyQuil's effects typically last about 4 to 6 hours, with drowsiness possibly extending up to 8 hours or longer depending on individual factors like metabolism, age, liver function, and dosage
. Complete elimination of NyQuil from the body can take between 24 to 48 hours, and in some cases up to 2 to 3 days, especially considering the longest-lasting ingredients like doxylamine and dextromethorphan
. Factors influencing how long NyQuil stays in your system include:
- Metabolism speed
- Liver function
- Age and weight
- Dosage and frequency
- Use of alcohol or other medications
In summary, while NyQuil's symptom-relief effects wear off within 4 to 6 hours, the medication can remain detectable and active in your system for up to 1 to 3 days depending on the individual and specific product formulation.
