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.

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).

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.

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.

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).

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).

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.