Side Effects of Nyquil

Side Effects of Nyquil

Jan 11

Nyquil is an over-the-counter medication commonly used for the relief of symptoms that occur with viral upper respiratory illnesses and allergies.  There are many different formulations of Nyquil, for example Nyquil D, NyQuil Sinus, NyQuil Cough, and NyQuil Cold/Flu Multisymptom Relief.

The spectrum of side effects associated with each Nyquil formulation will vary slightly due to the fact that each Nyquil product contains different active ingredients.  The active ingredients that are used in Nyquil products can include:

Acetaminophen- Also known as Tylenol or Paracetamol, Acetominophen is an over-the-counter pain reliever and fever reducer.

Doxylamine succinate– This ingredient is an antihistamine that is used for temporary relief of rhinorrhea, sneezing, lacrimation, itching eyes, or oronasopharyngeal itching associated with allergic rhinitis (e.g., hay fever) or other upper respiratory allergies.  However, doxylamine is also very sedating and is occasionally used in the short term treatment of insomnia.

Phenylephrine– This is a nasal decongestant used in many over-the-counter syrups, capsules and nasal sprays.

Dextromethorphan– This is a very common over the counter cough suppressant.

Pseudoephedrine– This a nasal decongestant.  However, due to abuse potential, formulations that contain pseudoephedrine in the United States are now available only by asking a pharmacist.

The inactive ingredients of the Nyquil preparations will vary, as will the particular combination of the above active ingredients that is used in each Nyquil formula.  However, there is one ingredient that is consistent through out all available formulations of Nyquil.

The ingredient that is in all Nyquil products and could, thus, most accurately be considered to represent “Nyquil” is Doxylamine succinate.  This is a first generation antihistamine that is associated with numerous side effects and contraindications.

The adverse effects consistently associated with Nyquil include:

-Possible paradoxical excitement in children.  Symptoms include restlessness, insomnia, tremors, euphoria, nervousness, delirium, heart palpitations, and seizures.

-Possible increased risk of dizziness, sedation, and hypotension (low blood pressure) in the elderly.

-Risk of severe drowsiness, meaning that extreme caution should be used when driving a motor vehicle or operating machinery.

-Possible anticholinergic effects such as dryness of mouth, nose, and throat, pain during urination, and urinary retention.

-Patients with glaucoma, respiratory conditions such as asthma, emphysema and chronic bronchitis, or difficulty urinating due to prostatic hypertrophy should consult their physician before self-treating with any Nyquil product.

Nyquil has many ingredients associated with a variety of side effects.  In particular, the adverse affects of the main ingredient, Doxylamine succinate, should be taken into consideration when using any of the available Nyquil products.


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