When You Take Too Much NyQuil, This Is What Happens

Proctor & Gamble, which manufactures Vick's NyQuil, likes to call its selection of NyQuil-branded multi-symptom cold medication "the nighttime sniffling, sneezing, coughing, aching, stuffy head, fever, so you can rest medicine" (per Twitter). Indeed, when a cold or flu (or COVID-19) interferes with getting a good night's sleep, many do turn to NyQuil, according to YouGov, which puts the brand's recognizability at 98% and popularity at 69% — making NyQuil the fourth most popular drug brand, behind Band-Aid, Neosporin, and Benadryl, and the most popular multi-symptom cold medication brand.

Of the top four, only NyQuil targets a broad array of symptoms associated with common upper respiratory infections, including fever and ache, cough, and nasal congestion, while also helping to induce drowsiness (via Healthline). NyQuil's Cough, Cold & Flu formula is the standard-bearer, with the Severe formula promising additional relief. In addition, NyQuil comes in Cough-and-Congestion-only formula, a formula designed for Kids (over the age of six), a formula designed for those with high blood pressure, and even an alcohol-free formula. 

It goes without saying that you shouldn't take more than the recommended dose or otherwise use NyQuil except as directed — which is to say, as a drowsiness-inducing cold and flu relief medication. In fact, the FDA has issued a specific warning against the so-called "NyQuil Chicken Challenge" that's made the rounds on social media (via The New York Times). Here's why you should take that advice to heart, and what can happen if you take too much NyQuil.

All NyQuil medications address multiple cold and flu symptoms by combining several active ingredients into a single formula. All NyQuil products contain the cough suppressant, dextromethorphan (DXM), the active ingredient in many cough medicines (per WebMD). The Alcohol-Free formulation contains about one-third more DXM than the others, and the Kids formulation contains about one-quarter less. DXM is also known to cause slight drowsiness.

Also contributing to NyQuil's drowsiness factor is an antihistamine. All formulations except for Alcohol-Free and Kids contain 12.5 milligrams of the antihistamine doxylamine succinate (DS). Both the Alcohol-Free and Kids formulas use chlorpheniramine maleate (CM); CM is safe for children, whereas DS is not, per Parkview Health. The Kids formula contains half as much CM as Alcohol-Free. Both of these active antihistamine ingredients are also intended to relieve runny nose and sneezing, according to Vicks. Although both have a sedating effect, CM's is less pronounced, according to Parkview Health. 

In addition to an antihistamine, both the Severe and Cough-and-Congestion formulations also contain the active ingredient phenylephrine, which MedlinePlus characterizes as a non-antihistamine decongestant. Phenylephrine may be better at relieving congestion associated with cold/flu, but it doesn't cause drowsiness. Finally, all formulations except for Cough-Only and Kids contain acetaminophen (650 milligrams per dose). Acetaminophen, which also isn't associated with drowsiness, is a common pain reliever and fever-reducer that is available over the counter. 

Codeine is an effective pain-reliever and cough-suppressant, according to the FDA. Codeine, which is considered a psychotropic drug because it does what it's good at doing (i.e., pain relief and cough suppressing) by way of depressing the central nervous system (CNS), per the National Institute on Drug Abuse (NIDA). Depressing the CNS comes at the risk of breathing problems, which can sometimes be life-threatening (via MedlinePlus). In addition, codeine, being an opioid drug, is also potentially habit-forming, per Narconon. 

Accordingly, scientists learned how to manufacture DXM (which isn't an opioid, although it's chemically related), per the U.S. Department of Justice. DXM, which is widely available without a prescription, quickly came to supplant codeine as the most popular cough suppressant in the U.S. DXM is the cough suppressing ingredient in NyQuil, which was first brought to market in 1966 (via Vicks), a decade after scientists had already begun to manufacture DXM. 

While codeine is not part of any NyQuil formulation, some of NyQuil's active ingredients have been associated with psychotropic effects. These include acetaminophen (per Wired) and, interestingly enough, DXM (per DEA).

The fact that NyQuil comes in an at least one Alcohol-Free formulation (the High Blood Pressure formulation is also alcohol-free, per Instagram) may already have tipped you off that, by default, liquid NyQuil does contain alcohol (per Vicks). Alcohol is not an active ingredient in NyQuil, according to Drugs; it's there solely to help the other ingredients to dissolve. On the other hand, alcohol comprises 10% of NyQuil's volume, per HelloPharmacist. If that sounds like a lot, that's because it is. To wit, it's more than the alcohol volume of beer. 

Nevertheless, the amount of alcohol in a single recommended dose of NyQuil — which, for adults, is 30 milliliters, or around one ounce — is unlikely to cause intoxication in adults. As HelloPharmacist points out, 10% of 30 ml is equal to three grams of alcohol. Three grams of alcohol is less than one-quarter of the alcohol content of a standard mixed drink (or single serving of beer or wine) — i.e., 14 grams, according to the National Institute on Alcohol Abuse and Alcoholism. 

On the other hand, the presence of even this small amount of alcohol may be problematic to those who cannot tolerate alcohol for whatever reason, including a pre-existing addiction or any condition or medication that interferes with the body's ability to metabolize alcohol (per Hello Pharmacist). Moreover, the alcohol content in NyQuil becomes more problematic to the extent that you take too much NyQuil.  

For all NyQuil brand multi-symptom cold and flu products except for the Kids formula, the recommended dosage for adults and children over the age of 12 is 30 milliliters every six hours, not to exceed more than four doses in 24 hours, according to the Vicks NyQuil FAQ. For the Kids formula, the recommended dosage is 15 milliliters every four hours for kids between the ages of six and 12, and 30 milliliters every four hours for adults and children over the age of 12, in each case not to exceed four doses in 24 hours. 

Taking more than the recommended dosage of NyQuil can cause symptoms of overdose. But even if you don't start out with the intention of taking too much NyQuil, The Recovery Village points out that if you're taking NyQuil on a nightly basis, you may run the risk of developing an increased tolerance to its active ingredients. What that means is that you will need more NyQuil to achieve the same level of relief — particularly if the relief that you're seeking is from insomnia. Increased tolerance suggests physical dependence, which can lead to addiction (per Addiction Center).

NyQuil's labelling also does not specifically address addiction risk. But it does warn against taking NyQuil for more than a week to relieve cold/flu symptoms — the reason being that lingering symptoms should be addressed by a healthcare professional.

For certain individuals, any NyQuil is too much. This is true for anyone who is allergic to any of its ingredients. It's also true for children under age four (per Vicks NyQuil FAQ). Children between four and six should only take NyQuil's Kids formula, and only if prescribed by a doctor. Likewise, NyQuil is contraindicated for anyone taking monoamine oxidase inhibitor (MAOI) drugs or has done so within the last 14 days (via DailyMed), and for anyone with high blood pressure (save for NyQuil's High Blood Pressure formula, per Instagram). 

Others for whom any Nyquil is too much include anyone regularly taking a medicine containing acetaminophen (because this increases risk of acetaminophen overdose), anyone with a history of liver disease (because acetaminophen can cause liver toxicity, especially when combined with alcohol, which NyQuil contains), and anyone who regularly consumes more than three alcoholic beverages per day, according to Drugs. Even if you don't drink alcohol regularly, NyQuil can be harmful if you drink any alcohol while taking it, per Healthline, which explains that any of the active ingredients in NyQuil have the potential to interact adversely with alcohol. 

Any NyQuil may be dangerous for individuals with certain other medical conditions (including pregnancy) or who are taking certain other substances, including potassium (per Drugs), cannabinoids (via Healthline), or other sleep aids (also per Healthline). Your healthcare provider should be able to tell whether you can safely take NyQuil.

Assuming it's safe for you to take any NyQuil at all, one thing to be aware of before you down that first dose is how long its drowsiness effects could last. Although NyQuil can be taken every six hours, the drowsiness associated with DS, the antihistamine in most forms of NyQuil (except the Alcohol-Free and Kids formulations), can last longer, according to Drugs. After a single label-recommended dose, drowsiness may persist for up to eight hours. After multiple doses, even if taken precisely according to the directions on the label, drowsiness may persist even longer. 

Moreover, NyQuil may induce a hangover-like effect, according to Hangover Hospital Keywest, which states that "while NyQuil may provide relief at night, many people have trouble shaking the grogginess when they wake up." Hangover Hospital recommends coffee and hydration to combat the NyQuil hangover, and suggests that you may be able to avoid the hangover effect by taking NyQuil at smaller doses than the label suggests. 

At higher doses — i.e., doses that exceed that which the label or your own healthcare provider recommends — these aforementioned effects could be magnified. Further, it is possible to overdose on NyQuil.

Taking small doses of acetaminophen is safe. However, exceeding the recommended dosage could damage the liver, according to American Addiction Centers (AAC). Per MedlinePlus, to avoid liver damage, adults should never take more than 3,000 milligrams of acetaminophen in a single day (and even less for adults over age 65). Note: If you're taking the maximum recommended dosage of NyQuil (which contains 650 milligrams per dose), you may already be approaching the maximum you should be taking.

Potentially complicating matters is the fact that acetaminophen overdose symptoms may take 12 or more hours to present. Moreover, the early symptoms can feel a lot like flu symptoms, according to Piedmont Healthcare. These include gastrointestinal distress such as stomach pain and intestinal cramping, nausea, vomiting, and loss of appetite. These symptoms may be accompanied by fatigue and excessive sweating. As symptoms worsen, there may be pain in the upper right quadrant, signifying liver inflammation. Other more emergent signs of acetaminophen toxicity include dark urine, dark stools, pale skin, jaundice (i.e., yellowing of the skin and/or eyes), and unusual bleeding, according to AAC. 

Acetaminophen overdose may be further complicated because acetaminophen interacts with alcohol and other medications, including antibiotics, birth control pills, NSAIDS, and some medications used in the treatment of high blood pressure, high cholesterol, cancer, HIV/AIDS, and seizures. With repeat daily doses of acetaminophen, the risk of these interactions increases (via the Cleveland Clinic).

DS is an antihistamine that is also FDA-approved as a sleep-aid, per DailyMed. It's one of the active ingredients in NyQuil, and one of the major reasons why NyQuil can make you feel sleepy. Sleep can be induced at dosages of DS as low as 6.25 milligrams, per a study presented at the 2007 Mediterranean Emergency Medicine Congress. The maximum dose of DS that may be taken by adults for runny nose and sneezing is 60 milligrams, according to the Prescriber's Digital Reference. When used solely as a sleep-aid, the maximum dose goes down to 25 milligrams.

NyQuil products with DS contain 12.5 milligrams per dose. That means that if you're taking NyQuil strictly for relief of cold or flu symptoms, you can safely take four doses per day without exceeding the maximum. However, if you're taking NyQuil solely as a sleep aid, taking more than two doses per day can be problematic, albeit not necessarily from an overdose standpoint. For individuals with pre-existing liver problems, the threshold for overdose may begin with lower dosages. Symptoms of DS overdose, in addition to excessive drowsiness, may include dilated pupils, weakness, flushing, and fever, and may progress to hallucinations, shaking and twitching, seizures, and loss of consciousness, per WebMD.

NyQuil's Alcohol-Free and Kids formulations swap out DS for chlorpheniramine maleate (CM), an antihistamine. Taking more than the recommended dose of CM can cause excessive drowsiness, nausea, blurred vision, heart palpitations, and seizures (via NHS).

In addition to an antihistamine, both the Severe and Cough-and-Congestion NyQuil formulations contain phenylephrine, which is the active ingredient in Sudafed. Something that you may not know about this particular decongestant, however, is that it is also used clinically to raise blood pressure in certain hypotensive individuals (via McGraw Hill Medical). Accordingly, any amount of phenylephrine — and formulations that contain it — may be contraindicated for individuals dealing with high blood pressure, per the Mayo Clinic. This is one reason why the NyQuil High Blood Pressure formulation contains no phenylephrine.

Ironically enough, given its use in a nighttime cold medication, the side effects of phenylephrine — even at recommended dosage levels — may include sleeplessness, nervousness, shaking, and increased heart rate, according to WebMD. Other side effects may include headache, dizziness, lightheadedness, headache, and upset stomach. Symptoms of phenylephrine overdose include the aforementioned side effects, as well as fainting, hallucinations, vomiting, and seizures. 

The cough suppressant DXM is considered safe at recommended dosages. A single dose of most NyQuil formulations contains 20 milligrams of DXM; the Alcohol-Free formulation contains 30 milligrams. At higher dosages, DXM may induce feelings of euphoria, according to Medical News Today. While feeling euphoric may not sound like such a bad thing, it has actually been found to be problematic because it may encourage recreational use of NyQuil, as well as combined use with alcohol — and it has been known to do so, especially among teenagers (via American Addiction Centers). 

Recreational use of medications containing DXM can lead to increased tolerance, according to a 2013 publication in the University at Buffalo's Clinical and Research Institute on Addictions. Increased tolerance means higher doses will be needed to achieve the same psychotropic effect. This can lead to DXM overuse, abuse, and eventual physical dependence (via a 2007 review published in Pharmacology).

As DXM dosage escalates, so too does the risk of serious adverse effects, including hot flashes, high blood pressure, involuntary eye movement, and seizures, rapid heart rate, difficulty breathing, kidney failure, as well as confusion, paranoia, agitation, and inappropriate affect (via Medical News Today). At doses exceeding 200 milligrams, DXM may induce dissociative effects such as sensory distortions and feelings of detachment (per the NYC Health Department) and even psychosis (via a case study in Addiction Biology).

Given that all of the active ingredients in the various NyQuil products are capable of causing overdose, it stands to reason that taking too much NyQuil can lead to overdose. 

"Yes, you can overdose on NyQuil if you take more than recommended, give a child more than is recommended, or you give NyQuil to a child who is under the age of 6 years," Drugs.com confirms. An overdose can occur from a single dose of NyQuil. However, an overdose can also occur down the line, as tolerance to its active ingredients escalates, requiring higher doses to achieve the same effects. 

Symptoms of Nyquil overdose include all of the aforementioned symptoms of overdose with regard to NyQuil's various active ingredients, including gastrointestinal distress, hot flashes, extreme tiredness, altered mental state, jaundice, dark urine/stool, difficulty breathing, and seizures, per WebMD. In children, one of the first signs of NyQuil overdose may be overexcitement. If you notice any of these symptoms in connection with taking NyQuil, it is important that you seek emergency treatment as quickly as possible, because NyQui overdose can be fatal (per Drugs.com). In addition to calling 911, you may be able to obtain assistance by calling your local poison control center at 1-800-222-1222.

When you take NyQuil correctly (i.e., according to the directions on the label), there is little risk of becoming addicted, according to Addiction Center. However, when you take too much NyQuil, whether by taking too much in a single dose or by taking it for the wrong reasons (e.g., as a long-term sleep aid or for the purpose of getting high) potentially leading to regular use over an extended period, your risk of becoming addicted increases. This is primarily due to the fact that all NyQuil formulations contain the cough suppressant DXM, and DXM use can escalate into increased tolerance, physical dependence, and eventual addiction (via a 2007 review published in the journal Pharmacology). 

As with other substance addictions, NyQuil addiction can lead to physically uncomfortable withdrawal symptoms. As Addiction Center points out, "When a person starts to experience withdrawal symptoms when they put NyQuil back in the medicine cabinet, NyQuil dependence has escalated into NyQuil addiction." Aside from cravings for NyQuil, symptoms of NyQuil withdrawal include depression, insomnia, chills, anxiety, restlessness, shaking, tremors, stomach pain, and nausea. 

If you've been taking too much NyQuil and have begun to experience withdrawal symptoms or other symptoms of physical dependence/addition, it's important to seek medical support and/or rehab, which can help ensure recovery. In some cases, medically supervised detox may be warranted.