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How Long Does DayQuil Stay In Your System?

DayQuil is an over-the-counter (OTC) medication sold by Procter & Gamble under the brand “Vicks.”  It is manufactured in approximately 5 formulations, each of which contain a unique set of ingredients aimed to target a specific symptom (e.g. coughing) or multiple symptoms as one would experience with the common cold and/or influenza.  DayQuil is considered similar to its sister compound NyQuil, but unlike NyQuil which is intended for nighttime usage, DayQuil is meant to be taken during waking hours.

Common ingredients within DayQuil formulations include: dextromethorphan (DXM), acetaminophen, phenylephrine, guaifenesin, and oxymetazoline.  Some formulations solely contain dextromethorphan, while others contain a specific mixture of two, three, or four of the aforementioned chemicals.  Dextromethorphan is effective as an antitussive (cough suppressant), acetaminophen acts as an analgesic and reduces fevers, guaifenesin increases mucus expulsion, while both phenylephrine and oxymetazoline act as decongestants.

The popularity of DayQuil has continued to increase due to the fact that it alleviates unwanted symptoms [associated with a variety of sicknesses] without significantly compromising alertness, cognitive function, and vigilance.  However, many users may still experience some slight brain fog or report side effects even after they’ve stopped DayQuil for a few days.  This has lead some individuals to question how long DayQuil stays in their system upon cessation.

How long does DayQuil stay in your system?

If you recently stopped taking DayQuil and are over your sickness, you may notice that some side effects you experienced while taking DayQuil continue to linger.  As a result of these lingering effects, you may suspect that DayQuil is still in your system.  To determine whether DayQuil is likely in your system, you’ll first need to determine the specific DayQuil formulation that you had utilized.  Below is a list of various DayQuil formulations.

  • DayQuil Cough (Dextromethorphan)
  • DayQuil Cold & Flu (Acetaminophen, Dextromethorphan, Phenylephrine)
  • DayQuil Severe Cold & Flu (Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine)
  • DayQuil Mucus Control DM (Dextromethorphan, Guaifenesin)
  • Dayquil Sinex (Acetaminophen, Phenylephrine, or Oxymetazoline)

As you can see, some formulations such as DayQuil Cough only contain the ingredient dextromethorphan, whereas others such as DayQuil Severe Cold & Flu contain several ingredients including acetaminophen, dextromethorphan, guaifenesin, and phenylephrine.  To accurately determine how long each DayQuil formulation stays in your system, it is necessary to examine the elimination half-lives of the full set of ingredients.  Below is a list of each ingredient with its respective elimination half-life.

  • Acetaminophen: 1 to 4 hours
  • Dextromethorphan: 3 to 6 hours
  • Guaifenesin: ~1 hour
  • Oxymetazoline: 1.72 to 2.32 hours
  • Phenylephrine: 2 to 3 hours

Knowing the elimination half-lives of DayQuil ingredients, we can estimate that formulations containing dextromethorphan may take the longest to eliminate.  This is because dextromethorphan may exhibit an elimination half-life of 3 to 6 hours, indicating that it may take up to 33 hours to completely clear it from the plasma.  Another popular ingredient within certain DayQuil formulations is that of acetaminophen which has a half-life from 1 to 4 hours.

This suggests that systemic elimination of acetaminophen could take up to 22 hours.  Of all potential DayQuil ingredients, Guaifenesin has the shortest elimination half-life of ~1 hour, meaning it will be out of your system in less than 6 hours post-ingestion.  Oxymetazoline is also eliminated quickly in under 13 hours (on average) and Phenylephrine should be out of a DayQuil user’s system within 16.5 hours.

Knowing the approximate elimination times of DayQuil ingredients, we can conclude that most users should have cleared DayQuil from their systems within 24 to 48 hours of their final dose.  Much of the elimination speed among formulations containing dextromethorphan will be contingent upon CYP2D6 isoenzyme function.  Individuals who are CYP2D6 poor metabolizers may take considerably longer than usual to eliminate this ingredient within DayQuil.

That said, only a small percentage of the population are classified as CYP2D6 poor metabolizers.  Therefore we can expect a majority of DayQuil users (assuming no other health problems) to eliminate the ingredients from their systems within 1 to 2 days of their final dose.

  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/dextromethorphan
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/acetaminophen
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/phenylephrine
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/guaifenesin
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/22855901

Variables that influence how long DayQuil stays in your system

Most DayQuil users should expect to have eliminated the pharmacologically active ingredients from their systems within 24 to 48 hours of taking their final dose.  Though 24 to 48 hours is considered an “average” elimination timeframe, some users may eliminate DayQuil at a faster or slower pace than this average.  Variables that often influence how long DayQuil stays in a person’s system include: individual factors, dosage, frequency of administration, and simultaneously administered drugs.

  1. Individual factors

Two individuals could simultaneously administer the same single dose of DayQuil Cold & Flu, yet one user may metabolize and eliminate the ingredients from his/her system faster than the other.  Though most users will likely eliminate the ingredients from their respective “systems” in a similar amount of time, individual factors may alter elimination times.  These factors include things like: a person’s age, body mass, food intake, genetics, glutathione levels, hepatic function, and renal function.

Age:  The age of a DayQuil user may affect how long it’ll take to metabolize and eliminate pharmacological ingredients from systemic circulation.  Elderly individuals (over the age of 65) tend to have poorer overall physiologic function and exhibit altered distribution of DayQuil ingredients upon ingestion (compared to younger adults).  This altered disposition leads to an increase in plasma concentrations of ingredients like acetaminophen and impairs clearance.

Elderly individuals also are likely to exhibit declining hepatic and renal function, both of which may extend the elimination half-life of DayQuil compared to other users.  An array of other potential health conditions, concomitant medications, and decreased glutathione levels can also prolong systemic elimination of DayQuil.  For these reasons, it should be expected that younger adults will likely clear DayQuil from systemic circulation faster than elderly.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/7056022

Body mass + Fat (%): A user’s body mass and fat percentage may impact how long DayQuil is likely to remain in systemic circulation.  Individuals with a high BMI (especially relative to the dosage ingested) are likely to eliminate DayQuil quicker from their systems than those with a low BMI.  This is due to the fact that larger individuals can handle and metabolize larger doses with greater efficiency than smaller individuals.

Since most of the ingredients within DayQuil are hydrophilic, body fat percentage could also influence elimination speed.  Individuals with a high percentage of body fat are less likely to accumulate or retain hydrophilic ingredients of DayQuil because they likely have less muscle and ultimately fewer water stores; this may force lipophobic ingredients to leave the body at a quicker rate.  Users with low body fat and more muscle may retain certain ingredients for a longer duration within tissue because they’re holding more water.

Genetics: A person’s genes can influence the hepatic function of CYP450 (cytochrome P450) isoenzymes that are responsible for metabolizing various components of DayQuil.  Although most ingredients are unlikely to be affected by genetic polymorphisms, dextromethorphan metabolism may be altered among those with CYP2D6 polymorphisms.  Specifically, individuals with alleles that decrease CYP2D6 isoenzyme function may retain dextromethorphan for a substantially longer term than those with normative CYP2D6 function.

Research suggests that elimination half-life of dextromethorphan among those considered “CYP2D6 poor metabolizers” may be around 19 hours.  If you are a CYP2D6 poor metabolizer (3% to 10% of the population), you may be unable to clear dextromethorphan (within DayQuil) from your system for up to 5 days after ingestion.  On the other hand, if you are a CYP2D6 rapid metabolizer, you may eliminate the dextromethorphan (within DayQuil) from your system in less than 2 days.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/8841152

Glutathione levels: The pharmacokinetics of DayQuil formulations with acetaminophen may be affected by an individual’s glutathione levels.  Acetaminophen is metabolized via conjugation with glucuronides and sulfates prior to elimination.  When taken at high doses, the conjugation processes are overwhelmed and it requires CYP450 isoenzyme metabolism, converting acetaminophen to a toxic metabolite “NAPQI.”

NAPQI isn’t a major problem among those with sufficient levels of the antioxidant glutathione.  This is because is undergoes conjugation with glutathione and the NAPQI is neutralized and eliminated.  However, among high-dose DayQuil users with low glutathione, it is possible that elimination of acetaminophen and its NAPQI intermediary metabolites will be impaired.  For this reason, those with low glutathione should be expected to eliminate acetaminophen slower than those with high levels.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/3829578

Hepatic function: Though not all of the ingredients within DayQuil undergo extensive hepatic metabolism, it is necessary to consider that hepatic impairment may prolong elimination of certain ingredients.  Research shows that among individuals with hepatic impairment, its elimination half-life may exceed 4 hours.  This means that it could take longer than a full day to fully eliminate acetaminophen from systemic circulation.

Elimination of dextromethorphan within DayQuil is likely to be prolonged to a greater extent than acetaminophen among those with hepatic impairment.  This is due to the fact that dextromethorphan is metabolized primarily by CYP2D6 isoenzymes and the function of these enzymes may decrease in respect to the degree of impairment.  Elimination of dextromethorphan among those with severe hepatic impairment could exceed 5 days.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/499292

Metabolic rate: Your BMR (basal metabolic rate) can affect how quickly various drugs are metabolized and excreted from systemic circulation.  Individuals with high BMRs are burning more energy at rest, and ultimately eliminate exogenous substances faster from their plasma than those with low BMRs.  This is evidenced by those with hyperthyroidism, a condition that radically amplifies BMR, leading to rapid metabolism of drugs.

Those with a low BMR are burning less energy at rest, and are less physiologically primed to metabolize and eliminate the ingredients within DayQuil.  Though BMR may affect elimination speed of DayQuil, it is unlikely to be of notable significance unless a user has hyper- or hypo-thyroidism.  That said, if you have a high BMR, you may eliminate DayQuil slightly quicker than someone with a lower BMR.

Renal function: Upon ingestion of DayQuil, its ingredients such as acetaminophen and dextromethorphan are metabolized and the metabolites are conjugated into glucuronides and/or sulfates prior to elimination.  These conjugated metabolites are processed by the kidneys and eliminated primarily through the urine.  Among those with suboptimal kidney function and/or renal impairment, it is possible that clearance speed and elimination half-life could be prolonged.

Renal impairment often leads to accumulation of metabolites within the kidneys, followed by reabsorption and recirculation throughout the system.  If you have normative renal function, the clearance and urinary excretion of metabolites should be efficient.  However, those with impairment may exhibit compromised efficiency of renal excretion – leading to longer systemic retention of DayQuil.

Urinary flow rate: Your urinary flow rate could also influence how quickly DayQuil gets eliminated from your system.  Individuals with a high urinary flow rate will likely excrete a greater amount of acetaminophen in a shorter duration than those with a low urinary flow rate.  Since hydration is known to have an impact on urinary flow rate, perhaps the degree to which you stay hydrated while using DayQuil will determine how long it remains in your system upon discontinuation.

Someone who maintains optimal hydration should excrete DayQuil with greater efficiency than an individual who is dehydrated or suboptimally hydrated.  Though urinary flow rate can influence the excretion of acetaminophen, it is unknown as to whether it affects excretion of other DayQuil ingredients such as dextromethorphan.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/2257860
  1. Daily dosage

The total daily dosage that you take of DayQuil will likely affect how long it remains in your system after your final dose.  Let’s assume that you decided to take “DayQuil Cold & Flu” which contains: 325 mg acetaminophen, 10 mg dextromethorphan, and 5 mg phenylephrine – per dose.  If you were to take 4 doses within 24 hours, your body would need to metabolize and eliminate 1300 mg acetaminophen, 40 mg dextromethorphan, and 20 mg phenylephrine.

On the other hand, if you were to only take 2 doses, you would only have ingested 650 mg acetaminophen, 20 mg dextromethorphan, and 10 mg phenylephrine.  When dosages are increased, the metabolism and elimination of various ingredients becomes less efficient.  This is because with high doses, hepatic enzymes are taxed to a greater extent; there’s a greater quantity of an exogenous substances that needs to be metabolized.

Furthermore, there are a greater number of metabolites formed in the process, possibly leading to increased accumulation within plasma.  As a result of the increased plasma concentrations and metabolite formation among high dose users, efficiency of renal excretion is reduced.  The kidneys are only capable of eliminating a certain amount of the DayQuil ingredient metabolites at a time.

Low dose users are unlikely to tax metabolic pathways to the same extent as high dose users and exhibit lower plasma concentrations.  Additionally, renal excretion should remain efficient among low dose users because there’s a reduced amount of the exogenous substance that necessitates excretion.  Therefore if you are a low dose DayQuil user, you may clear its ingredients faster from your system than a high dose user.

  1. Frequency/Term of administration

The term and frequency of DayQuil administration may be necessary to consider when determining how long it is likely to stay in your system.  If you simply used a single dose of DayQuil one day when you were sick, it is likely to get eliminated efficiently from your system.  However, if you were frequently administering DayQuil several times per day for a long-term (e.g. several weeks), it may take longer for your body to eliminate it.

A high-frequency user such as someone ingesting DayQuil several times per day is forcing their body to metabolize an additional dosage before the previous one has been metabolized and cleared from the plasma.  This means that a frequent user is likely to accumulate DayQuil ingredients (as well as metabolites) within plasma, leading to slower hepatic metabolism and renal excretion.  Conversely, an infrequent user is unlikely to accumulate DayQuil ingredients within his/her system because there are gaps between doses.

These longer gaps between doses among infrequent users allows the body to fully eliminate the previous dose before another one is introduced.  Therefore if you use DayQuil on an inconsistent basis, expect a faster elimination than someone using it every day, several times per day.  The term of administration or total duration over which DayQuil was taken may also affect its elimination speed.

A frequent user of DayQuil that has been taking it daily for a full year is likely to have accumulated a greater amount of the ingredients in his/her system than a short-term user.  In part this is because long-term users build up tolerance to lower doses of ingredients over time, leading to usage of higher doses.  The higher doses among long-term users are thought to increase ingredient accumulation and prolong elimination.

  1. Co-administered drugs (CYP2D6)

It is likely that co-administration of various drugs can affect how long DayQuil stays in your system.  In particular, the pharmacokinetics of DayQuil formulations containing dextromethorphan are likely to be altered by co-administration of drugs that affect function of CYP2D6 isoenzymes.  Drugs that interfere with CYP2D6 isoenzyme function are known as “inhibitors,” and are thought to prolong elimination of the dextromethorphan within DayQuil.

Examples of such CYP2D6 inhibitors include: Bupropion, Cinacalcet, Fluoxetine, Paroxetine, Quinidine, and Ritonavir.  Should you have taken any of these agents along with DayQuil formulations, realize that it’ll take longer to clear dextromethorphan from your system.  This is because CYP2D6 inhibitors downregulate function of CYP2D6 isoenzymes.

If you took a drug that enhanced CYP2D6 isoenzyme function, you should eliminate dextromethorphan (within DayQuil) faster than average.  Drugs known as CYP2D6 inducers increase activity of CYP2D6 isoenzymes within the liver, leading to faster metabolism and quicker systemic elimination.  Examples of CYP2D6 inducers include: Dexamethasone, Glutethimide, and Rifampicin.

DayQuil: Absorption, Metabolism, Excretion (Details)

Since DayQuil formulations may contain any variety of ingredients, it is necessary to analyze the pharmacokinetics of all potential DayQuil ingredients.  Ingredients within any given DayQuil formulation may include: acetaminophen, dextromethorphan,  guaifenesin, oxymetazoline, and phenylephrine.  Below is a brief pharmacokinetic description of each aforementioned ingredient.


Following administration of acetaminophen within DayQuil, it is rapidly absorbed within the gastrointestinal (GI) tract and undergoes hepatic metabolism.  Hepatic metabolism consists primarily of glucuronidation and sulfation of the parent acetaminophen.  Metabolites formed in the process include: APAP-gluc (acetaminophen glucuornide) and APAP-sulf (acetaminophen sulfate).  A small percentage of NAPQI may also form if glutathione levels are low and/or high doses of DayQuil are ingested.

The standard elimination half-life of acetaminophen ranges from 1 to 4 hours, indicating that it is usually out of your system within 22 hours. An estimated 90% of an acetaminophen dosage will be eliminated within urine in under 24 hours, primarily as APAP-glucuronides and APAP-sulfates.  Only a minimal amount of acetaminophen will be excreted unchanged (unmetabolized) within the urine.


The dextromethorphan within DayQuil will be rapidly absorbed via the gastrointestinal (GI) tract.  After dextromethorphan is absorbed by the GI tract, it is subject to extensive hepatic metabolism, primarily via CYP2D6 isoenzymes.  Hepatic metabolism (catalyzed via CYP2D6) converts dextromethorphan to its principal metabolite dextrorphan.

Peak serum concentrations of dextromethorphan are attained approximately 2.5 hours post-ingestion.  Concentrations of the dextrorphan metabolite peak within the bloodstream in around 1.7 hours after dextromethorphan ingestion.  Among those with CYP2D6 polymorphisms as to compromise CYP2D6 isoenzyme function, metabolism of dextromethorphan is reduced and ultimately less dextrorphan is formed.

Among extensive CYP2D6 metabolizers approximately 15% of a dextromethorphan dose forms minor metabolites such as D-methoxymorphinane.  Dextromethorphan and its metabolites are then subject to renal excretion.  Depending on CYP2D6 expression, up to 11% of a dose may be excreted unchanged as dextromethorphan, while in others, up to 100% of a dose may consist of metabolites.

Only a small amount of the dose is eliminated via feces (0.1%).  The elimination half-life of 3 to 6 hours suggests that dextromethorphan is likely to be out of a users system in under 33 hours.  Most users will have excreted the entire dosage within 24 hours of ingestion.


Guaifenesin is efficiently absorbed from the gastrointestinal tract and acts as an “expectorant” via maximizing volume and minimizing viscosity of trachea and bronchi secretions.  Following ingestion, approximately 60% of a dose is hydrolyzed within 7 hours.  It is converted primarily into the metabolite beta-(2-methoxyphenoxy)-lactic acid which appears within urine upon excretion.

Due to the fact that guaifenesin has a plasma elimination half-life of just 1 hour, it can be expected to be out of a users system much quicker than other ingredients within DayQuil.  Most of the guaifenesin ingested from DayQuil is eliminated as glucuronides and sulfates.  Therefore you should expect this ingredient out of your plasma in less than 12 hours.


Upon administration of DayQuil containing phenylephrine, the phenylephrine is completely absorbed and undergoes first pass metabolism within the intestinal wall and liver.  It is then rapidly distributed throughout the body to peripheral tissues.  Some speculate that phenylephrine could accumulate within organs, especially if administered frequently.

It has an estimated oral bioavailability of 38%, with its serum concentrations peaking within 45 minutes to 2 hours post-ingestion.  Metabolism of phenylephrine occurs primarily via sulfate conjugation (within the intestinal wall) and oxidative deamination (via monoamine oxidase enzymes).  To a minor extent, phenylephrine undergoes glucuronidation.

The elimination half-life of phenylephrine is thought to range between 2 and 3 hours, indicating that it is out of the plasma in under 17 hours.  Phenylephrine is processed by the kidneys and subject to urinary excretion.  In less than 48 hours, most individuals should have eliminated over 80% of a phenylephrine dose within urine; 2.6% of which is unchanged phenylephrine and the majority of which is phenylephrine metabolites.

  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/dextromethorphan
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/acetaminophen
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/phenylephrine
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/guaifenesin
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/22855901

Tips to clear DayQuil from your system

If you’ve recently stopped taking DayQuil and want to ensure that it is eliminated from your system as quickly as possible, below are some suggestions that may be helpful.  Prior to implementing any of these suggestions, be sure to verify safety and alleged efficacy with a medical professional.  Realize that not everyone will derive significant benefit from these tips in regards to expediting the elimination of DayQuil.

  1. Activated charcoal: A supplement that binds to unmetabolized chemicals and other endotoxins circulating throughout your body is activated charcoal. If you are concerned that any DayQuil may be lingering in systemic circulation, especially the acetaminophen component or its toxic metabolite “NAPQI,” you may want to take some activated charcoal. Activated charcoal carries a negative electrical charge allowing it to bind to any DayQuil remnants in your body that warrant elimination.
  2. Calcium-D-Glucarate: Based on the pharmacokinetic data from the ingredients of DayQuil, it is apparent that most ingredients are eliminated via renal pathways. If renal pathways are overtaxed as a result of environmental, dietary, or chemical toxins – accumulation of DayQuil may occur. To help out your kidneys, supplementation with calcium-d-glucarate may provide benefit.  Calcium-d-glucarate acts as a beta-glucuronidase inhibitor which releases molecules (e.g. ingredients of DayQuil) from detoxification pathways.
  3. Glutathione: Anyone taking large doses of DayQuil with acetaminophen should supplement with exogenous glutathione. Glutathione is generated by your liver and aids in the conjugation of acetaminophen metabolite NAPQI. Without enough glutathione to conjugate NAPQI, your liver may endure some damage and/or fail to eliminate acetaminophen in a timely manner.
  4. Urinary flow rate: Evidence suggests that elimination of acetaminophen (and possibly other DayQuil ingredients) may be influenced by urinary flow rate. The greater an individual’s urinary flow rate, the faster acetaminophen will be eliminated, whereas the lesser a person’s urinary flow rate, the slower the acetaminophen will be excreted. Urinary flow rate can be manipulated in large part via hydration.  If you stay optimally hydrated, you may excrete DayQuil quicker than if you were dehydrated.

How long has DayQuil stayed in your system after stopping?

If you’ve used DayQuil to treat symptoms of a common cold, influenza, nasal congestion, etc. – mention the dosage you were taking and the number of consecutive days over which you took it.  Share a comment mentioning whether you believe the DayQuil stayed in your system for more or less than 24 hours after your final dose.  If you believe it took a considerably longer duration than 24 hours to eliminate ingredients of DayQuil, support your hypothesis by sharing variables that may have prolonged elimination (e.g. renal impairment).

Realize that DayQuil formulations with dextromethorphan are likely to stay in a users system for a longer duration than average only if that individual happens to be a poor CYP2D6 metabolizer.  In this case, elimination could take up to 5 days, whereas among a normative metabolizer, elimination should take between 17 and 33 hours.  The bottom line though is that nearly every ingredient within common DayQuil formulations should be out of your system within 48 hours of your last dose.

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