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Generic Name: Acetylcysteine (oral) [a-SEET-il-SIS-teen].
The Brand Names: NAC, N-A-C Sustain.

What is NAC?

NAC is used to reduce or prevent the damage to the liver that is caused by the use of large amounts of acetaminophen (Tylenol). There are different types and brands of acetylcysteine available, and they are available from a pharmacy. Certain kinds of NAC can be effective as an antidote to acetaminophen. Don't try to treat an acetaminophen overdose without medical assistance. NAC is also employed for reasons not mentioned in this guide to medication.

Side effects of NAC

See a doctor immediately. If you are experiencing symptoms that are warning signs of a reaction, such as difficulty breathing, hives, and swelling of your lips, face, and throat, NAC can cause severe adverse reactions. Contact your doctor immediately. If you suffer from:

  • Severe or ongoing vomiting.
  • Vomit or bloody vomit that resembles coffee grounds.
  • Indications that the medication may not be effective: stomach nausea, weight loss, dark urine, dark-colored stool, jaundice (yellowing of the eyes or skin).

Common negative side effects of NAC could include:

  • Nausea, vomiting, upset stomach.
  • Rashes.
  • Fever.

This is not a comprehensive list of possible side effects, and other side effects could be present. Consult your physician for advice regarding medical effects. You can report any adverse reactions to the FDA at 1-800-FDA-1088.


In an emergency situation, you might not be able to tell doctors about your health concerns. It is important that the doctor who cares for you following the incident knows that you've received NAC.

Before you take this drug

It is best not to take NAC if you have an allergy to it. If you are able to, before you receive NAC, inform your caregivers if you've ever suffered from:

  • A stomach ulcer.
  • The stomach or within the esophagus (esophageal varices).
  • High blood pressure in the event that you're following low-salt diets.
  • Congestive heart failure.
  • Kidney disease.

Consult a physician before taking this medication if you are nursing or pregnant. In the event of an emergency situation, there is a chance that you will not be able to inform caregivers whether you're breastfeeding or pregnant. It is important that the doctor caring for your baby or your pregnant mother be aware that you have received this medication.

How to take NAC?

Follow the directions on the label or as directed by your physician. Do not use NAC if you do not understand the entire procedure. If you're in a medical emergency, Prior to taking NAC, medical professionals will conduct tests on your blood to assess the level of acetaminophen within your body. The test is most efficient when it is performed within 4–8 hours following an acetaminophen dose. If you're unable to recall when the last time you consumed acetaminophen was or the amount you took, you'll probably be given your first dose of acetylcysteine straight away. Your doctor will decide the length of time you will be treated with NAC. Don't discontinue taking NAC until the doctor advises you to. If you experience vomiting within one hour following taking NAC, you may have to take a second dose. Maintain at room temperature, free of heat and moisture.

What happens if I miss a dose?

You should take the medication as quickly as you are able, but do not take any missed doses if it's nearing the time to take the next dose. Don't take two doses at once.

What happens if I overdose?

Get medical attention in an emergency or contact the Poison Help line toll-free at 1-800-222-1222.

What should be avoided?

Follow the instructions of your physician regarding any limitations on foods, drinks, or any activity.

Interaction with other drugs

Other medications can influence NAC, such as prescription and over-the-counter medicines, vitamins, and herbal products. Discuss with your doctor your current medications as well as any medications you are about to start or stop taking