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What Are Mucinex's Inactive Ingredients?

Understanding What's In Your Medicine

Dr. Caryn Cassidy Profile Photo

Written by Dr. Caryn Cassidy on August 9, 2021

Mucinex is a popular medication that is best known for reducing chest congestion and suppressing cough associated with the common cold, flu, and other illnesses.

While you might be familiar with the active ingredients of Mucinex that help you stop coughing, you might not be familiar with the inactive ingredients, which can also cause adverse effects to some patients.

Before buying Mucinex, it’s important to know what are Mucinex’s inactive ingredients and what purpose they serve.

What is the difference between active and inactive ingredients?

All over the counter medications and prescription drugs contain two types of ingredients: active ingredients and inactive ingredients.

An active ingredient is defined by 21 Code of Federal Regulations (CFR) 210.3, Current Good Manufacturing Practice in Manufacturing, Processing, Packing or Holding of Drugs, Part (b)(7) as any component of a drug product that is intended to furnish pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body of humans or animals.

To put it simply, active ingredients are the part of the medication that actually makes you feel better by controlling your symptoms. For example, if you’re experiencing a runny nose, the active ingredient in the medication would be the ingredient that actually reduces your nasal congestion.

Under 21 CFR 210.3(b)(8), an inactive ingredient is defined as any component of a drug product other than the active ingredient. Approximately 75 percent of the average medication is composed of inactive ingredients, which help to shape the final look, feel, taste, and appearance.

According to Harvard Medical School, the average medication contains about nine different inactive ingredients.

  • Inactive ingredients can be used in medications for many different reasons, including:
  • Masking the bitter taste of some medications to make them easier to swallow
  • Preventing a medication from being dissolved
  • Binding the ingredients together to give the medicine a cohesive shape
  • Helping the body to absorb the drug more easily by combining with an easily digestible substance like a fatty acid
  • Preserving the medication by preventing the growth of bacteria and fungi

What are Mucinex’s active ingredients?

Mucinex is a national brand that produces many different formulas. While it is best known for its chest decongestants, each of the company’s formulas performs a number of different functions.

One of the most popular is Mucinex Maximum Strength Fast-Max Severe Congestion and Cough.

Mucinex Maximum Strength Fast-Max Severe Congestion and Cough contains the following active ingredients in each adult dose of 2 capsules.

  • Dextromethorphan HBr 10 mg
  • Guaifenesin 200 mg
  • Phenylephrine HCl 5 mg

Dextromethorphan HBr

Dextromethorphan HBr is an over the counter cough suppressant, or antitussive, that is used to temporarily stop coughing caused by the common cold, flu, and other medical conditions. The medication helps patients stop coughing by slowing down activity in the part of the brain that causes you to cough. While the medication is helpful in stopping coughing on a temporary basis, it does not treat the root cause of the cough or help the patient recover from any disease.


Guaifenesin is an over the counter medication that controls the symptoms of chest congestion. The medication belongs to a class of drugs called expectorants and works by making the mucus in the respiratory system thinner in order to allow the patient to cough it up more easily and expel it from the body. Like dextromethorphan, guaifenesin only treats symptoms and does not treat the root cause of chest congestion.

Phenylephrine HCl

The final active ingredient, phenylephrine HCl, is an over the counter nasal decongestant that helps to decrease postnasal drip, decrease nasal congestion, and improves your ability to breathe while you’re sick. Because postnasal drip can cause coughing and sore throat, you may also notice improvements in these symptoms as well.

What are Mucinex’s inactive ingredients?

Mucinex Maximum Strength Fast-Max Severe Congestion and Cough contains the following inactive ingredients: anhydrous citric acid, edetate disodium, FD&C Blue #1, FD&C Red #40, flavors, glycerin, propyl gallate, propylene glycol, purified water, sodium benzoate, sorbitol, sucralose, trisodium citrate dihydrate, and xanthan gum.

Glycerin serves multiple purposes in the product, acting as a thickening agent, a humectant, and a solvent. This inactive ingredient helps to improve the consistency of the caplets. Glycerin also helps to preserve foods and liquids, including medications, and it also provides sweetness to mask the bitter taste of the active ingredients.

Sodium benzoate, trisodium citrate dehydrate, propyl gallate, and anhydrous citric acid each work as different preservatives that help keep the medication free of potentially dangerous contamination. Sodium benzoate helps to prevent the growth of potentially harmful bacteria, yeast, and mold, while propyl gallate is an ester that helps to prevent oxidation. Anhydrous citric acid is a type of natural preservative that is used to inhibit the growth of bacteria and mold. Sodium citrate is a salt-form antiseptic that prevents the growth of some types of organisms and extends the shelf life of the product.

FD&C red no. 40 and FD&C blue no.1 are artificial dyes that add color to the medication. Typically, medications are colored in order to make them appear more palatable or to correspond to the flavor type advertised on the product.

Flavors are listed on the label of Mucinex Maximum Strength Fast-Max Severe Congestion and Cough, in order to make the medication easier to swallow.

Xanthan gum is the final inactive ingredient. This ingredient is used as a thickener or stabilizer.

Are inactive ingredients associated with any risks?

Pick up any medication, including both prescription drugs and over the counter treatments, and you are guaranteed to find a list of inactive ingredients on the label.

While the active ingredients of medications get the most attention because they work to treat your symptoms, it’s also important to consider inactive ingredients when choosing a medication, particularly if you have food sensitivities or have reacted poorly to medications in the past.

Although inactive ingredients are included in small quantities in most drugs, it is still possible to experience adverse effects from consuming the medication. Two of the most common risks associated with inactive ingredients in medications include the potential for allergic reactions and digestive distress due to intolerances.

Allergic reactions

Although allergic reactions to inactive ingredients are considered rare, they can be severe and potentially life threatening. Currently, 38 different inactive ingredients have been identified as having the potential to cause an allergic reaction, and nearly 93 percent of pills or capsules examined in one study were found to contain at least one potential allergen.

Inactive ingredients commonly found in medications that can cause an allergic reaction include:

  • Chemical dyes, such as yellow 5, FD&C red 40, and others
  • Peanut oil
  • Gluten (a protein found in wheat, barley, and rye)

If someone who is severely allergic to one of the inactive ingredients takes the medication, they could experience a life threatening allergic reaction known as anaphylaxis. Anaphylaxis causes swelling of the face, lips, and throat, difficulty breathing, and hives and can be fatal if the person does not receive treatment right away. Other symptoms of an allergic reaction include itching, skin irritation, and mild hives.

Inactive ingredients that are known to act as allergens include foods like gluten, lactose, cornstarch, peanut oil, and wheat starch; dyes like allura red, brilliant blue, and sunset yellow FCF; and sweeteners like aspartame, sucrose, mannitol, and saccharin.

Digestive distress

Some people are not allergic to inactive ingredients but may have difficulty digesting them as a result of food intolerances. The most common side effects associated with intolerance of inactive ingredients is digestive distress. The inactive ingredients most likely to cause digestive distress belong to a family of foods called FODMAPs, which stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

FODMAPs are substances that contain sugars that some people struggle to digest properly, which can cause symptoms like gas, diarrhea, and bloating. FODMAPs are commonly found in sugars that are used as inactive ingredients to improve the taste and mask the bitterness of the active ingredients. An estimated 55 percent of all oral medications include at least one FODMAP, with artificial sweeteners being the most common culprit.

Patients who take a number of different medications are more likely to experience adverse effects like allergic reactions or digestive distress. However, it is possible to experience an adverse effect even when taking just one medication if you are highly sensitive to one of the ingredients.


Mucinex produces many different formulas, but common active ingredients include dextromethorphan HBr, guaifenesin, and phenylephrine HCl.

Mucinex Maximum Strength Fast-Max Severe Congestion and Cough contains the following inactive ingredients: anhydrous citric acid, edetate disodium, FD&C Blue #1, FD&C Red #40, flavors, glycerin, propyl gallate, propylene glycol, purified water, sodium benzoate, sorbitol, sucralose, trisodium citrate dihydrate, and xanthan gum.

Some people may experience allergic reactions or digestive distress when exposed to certain inactive ingredients.