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Cold and Flu Center

NyQuil Overdose Symptoms

author image Matthew Busse
Matthew Busse has pursued professional health and science writing since 2007, writing for national publications including "Science Magazine," "New Scientist" and "The Scientist." Busse holds a doctorate in molecular biology from the University of California-San Diego.
NyQuil Overdose Symptoms
Red medicine in a measuring cup. Photo Credit: herreid/iStock/Getty Images

NyQuil can be used to treat the symptoms of a cold or the flu. Several varieties of the over-the-counter medication are available, each containing different combinations of medicines. A variety of symptoms may occur with a NyQuil overdose, depending on which type was taken and the amount. The severity of symptoms varies depending on the age of the person who took the medicine and how much was consumed. Symptoms usually begin within 30 minutes to 2 hours after ingestion. If taken in improper doses, each formulation of NyQuil can be toxic.

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Symptoms Related to Dextromethorphan

Dextromethorphan is a cough suppressant found in: -- NyQuil Cold and Flu. -- NyQuil D Cold and Flu. -- NyQuil Severe Cold and Flu. -- Alcohol-Free NyQuil Cold and Flu. -- Children’s NyQuil Cold and Cough. -- NyQuil Cough.

Frequent symptoms seen with an overdose of dextromethorphan include nausea, vomiting, dizziness, hallucinations, agitation, a sense of being detached from yourself and loss of coordination similar to what occurs with alcohol intoxication. Blood pressure and heart rate can also increase. Severe overdoses can lead to seizures, coma and even death. Occasionally, an overdose may also cause a condition called serotonin syndrome, with fever, sweating, chills, elevated blood pressure, and muscle spasms and rigidity -- which can lead to what has been described as a "zombielike" walking pattern.

Symptoms Related to Doxylamine and Chlorpheniramine

Several NyQuil products contain either doxylamine or chlorpheniramine, which are antihistamine medications. Products that contain one of these antihistamines include: -- NyQuil Cold and Flu. -- NyQuil D Cold and Flu. -- NyQuil Severe Cold and Flu. -- Alcohol-Free NyQuil Cold and Flu. -- Children’s NyQuil Cold and Cough. -- NyQuil Cough.

The alcohol-free and children's products contain chlorpheniramine. The others contain doxylamine. Drowsiness, dilated pupils, increased heart rate and blood pressure, fever without sweating, flushing, dry mouth, and disorientation or hallucinations are common symptoms of overdose with doxylamine or chlorpheniramine. Some people -- especially children -- become excited or irritable rather than drowsy and have difficulty walking normally. With more severe overdoses, extreme sluggishness or coma, a further increase in body temperature and seizures may occur.

Symptoms Related to Acetaminophen

Acetaminophen is a pain- and fever-relieving medicine found in: -- NyQuil Cold and Flu. -- NyQuil D Cold and Flu. -- NyQuil Severe Cold and Flu. -- Alcohol-Free NyQuil Cold and Flu.

While generally safe in recommended doses, acetaminophen overdoses can cause liver failure and death. Symptoms occur in stages. Initial symptoms of acetaminophen overdose are typically mild in the first 24 hours, including cramping, mild abdominal pain, nausea and vomiting. With high-level overdoses, significant liver damage and more severe symptoms develop 1 to 3 days after ingestion. At this stage, symptoms include more severe pain in the right, upper abdomen and yellowing of the skin and whites of the eyes, known as jaundice. The liver may fail, with uncontrolled bleeding, confusion, and sluggishness or coma. Death may occur.

Other Considerations, Warnings and Precautions

Liquid formulations of NyQuil not labeled alcohol-free contain 10 percent alcohol. Therefore, typical symptoms of alcohol intoxication can occur quickly. These include dizziness, nausea, vomiting, slurred speech and poor coordination. In addition, NyQuil Severe Cold and Flu contains the decongestant phenylephrine, and NyQuil D Cold and Flu contains the decongestant pseudoephedrine. These decongestants can cause high blood pressure and headaches in with low-level overdose, as well as seizures or brain bleeding with high-level overdose.

NyQuil should only be taken as directed and should not be taken with acetaminophen (Tylenol) or any other cold medications. Symptoms of a NyQuil overdose can vary because of the variety of ingredients. If overdose is suspected, seek emergency medical care. This is especially important for acetaminophen overdose. An antidote is available, but early treatment is crucial to preventing liver damage.

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