Acetylcysteine (Oral)

An oral medication, Acetylcysteine is used to reduce the risk of liver damage after an acetaminophen overdose.


Acetylcysteine is used to treat patients to prevent or lessen the risk of liver damage from acetaminophen overdose. This medication is taken only via the mouth and as directed by your doctor or physician, usually every four hours for the number of prescribed doses. The US brand names are Acys-5 and Cetylev. This medication is only available via a prescription from your official doctor.

Conditions treated

  • Prevent liver damage from acetaminophen overdose

Type of medicine

  • Oral tablet

Side effects

Along with the intended effects of taking Acetylcysteine, there can be some unwanted side effects. Many of these are not harmful and do not require medical attention, however, there are some side effects which are dangerous and if you recognise any of these symptoms in yourself, then you should contact your doctor or physician for medical advice about side effects. You can report any form of side effects to the FDA at 1-800-FDA-1088 or online via The side effects are listed below and are ranked in terms of common, less common and severe.

Most common

  • Nausea
  • Stomach pain
  • Vomiting
  • Rash
  • Fever

Less common

  • Difficulty in swallowing or breathing
  • Itching or hives
  • Nausea
  • Rash with or without a fever
  • Swelling of the face, eyes, or inside of the nose
  • Reddening of the skin, especially around the ears
  • Severe or ongoing vomiting

If any of these symptoms worsen, then contact your doctor immediately.


  • Severe abdominal and stomach pain
  • Bleeding from the stomach or intestines
  • Black stools
  • Vomit that has a resemblance to coffee ground

If any of these side effects are present, contact your doctor immediately and cease taking the tablet.


The final dosage of any tablet or medication will be decided between you and your doctor/physician. A specific dosage will usually depend on a variety of factors such as your age, height, weight and the amount of paracetamol that has been taken.

This medicine will be given to you by a health professional and can be whilst you are in the hospital. It works best when it is given as close to the time of overdose as possible. The longer the time delay from the overdose and receiving the medicine, the less effective it will be in protecting your liver. The effervescent tablets need to be dissolved in water before you take them and the mixed solution needs to be taken within two hours. Oral administration of this tablet requires dilution of the 20% solution with any type of diet soft drink such as diet cola to a final concentration of 5%.

Generally, there is usually a total of seventeen doses of this medicine and these are usually taken four hours apart. Be aware that if you vomit within 1 hour after consumption of the medicine, you will need to take an extra dose to make up for it.

The process

Step 1: Melt the tablet(s) in water as you have been directed by your physician. Do not swallow the tablet(s) whole.

Step 2: Drink the solution within 2 hours of mixing.

Step 3: Those who have feeding tubes may also use this medicine. Follow instructions from your doctor. Ensure that you flush the feeding tube after taking this medicine.

If you think there has been an overdose of Acetylcysteine, get medical care urgently or call your local poison control center. Be ready to explain what was taken, how much, and when it happened. US residents can call their local poison control center at 1-800-222-1222.


Drug interactions have the potential to increase your risk of serious side effects or change how your medications work. You need to ensure you keep a list of all the different drugs you use including herbal products and nonprescription/prescription drugs and share it with your physician and pharmacist. Under no circumstances should you stop, start or change the dosage of your medicine without the approval of your doctor beforehand.

There are six known drugs that can interact significantly with the consumption of Acetylcysteine and you should avoid taking these drugs when consuming Acetylcysteine.

  • A moderate reaction is caused by the use of Acetylcysteine and insulin, rapid action or inhaled.
  • Five known drugs to have a minor interaction with Acetylcysteine include: Charcol, Sorbitol, Simethicone, Ifosfamide and Mesna.

Other common medications checked in combination with Acetylcysteine include:

  • Vitamin B Complex 100 (multivitamin)
  • Aspirin Low Strength (aspirin)
  • Fish Oil (omega-3 polyunsaturated fatty acids)
  • CoQ10 (ubiquinone))
  • Paracetamol (acetaminophen)
  • Vitamin B12 (cyanocobalamin)
  • Vitamin B6 (pyridoxine)
  • Singulair (montelukast)
  • Vitamin D3 (cholecalciferol)
  • Vitamin C (ascorbic acid)

If you are taking any of the above medications, make sure you inform your doctor before you start taking Acetylcysteine.

Other interactions

Particular medicines cannot be used at or around the time of food consumption or eating a particular type of food since the risk of interactions can rise. The mixing of Acetylcysteine with tobacco or alcohol can lead to interactions also. It's therefore important that you discuss with your healthcare professional about the use of your medication in combination with alcohol, food and tobacco, as well as the other medicines listed above.


In addition to discussing what medications you are currently taking with your doctor or physician, the patient should also inform medical professionals of their past medical problems, including any current issues that are ongoing. There are a variety of warnings in place for the use of Acetylcysteine. Some of the most common warnings are listed below.

  • This medication contains sodium, so you should discuss with your pharmacist or doctor if you are on a diet which requires salt restriction or if you have a condition that could worsen if you eat more salt such as high blood pressure or heart failure.
  • As this medication can increase the risk of bleeding in your esophagus and stomach, you should tell your doctor or pharmacist your medical history of any bleeding in your esophagus or intestinal/stomach problems, such as ulcers.
  • With regards to pregnancy and breastfeeding, it's not known whether this medicine is harmful during pregnancy. However, an acetaminophen overdose could cause harm to both baby and mother, so the benefits of treating the overdose may not outweigh the risks associated with taking Acetylcysteine. You should, therefore, inform your doctor if you are pregnant. It's not known whether Acetylcysteine passes through to breast milk, so you should avoid breastfeeding whilst using this medicine.
  • Generalized urticaria has been observed rarely in patients receiving oral Acetylcysteine. If this should occur or there are signs and symptoms of other allergic reactions, then treatment with Acetylcysteine should cease unless it is deemed essential and the other allergic symptoms can be controlled by another means. If encephalopathy as a product of hepatic failure becomes evident, then Acetylcysteine should be discontinued to avoid any further consumption of nitrogenous substances.
  • This medicine contains levels of aspartame. Aspartame is a source of phenylalanine and is therefore potentially harmful to anyone who suffers from phenylketonuria.
  • This medicine also contains a specific coloring agent called sunset yellow (Ell0), which can cause significant allergic reactions.

Due to the warnings associated with taking Acetylcysteine, your doctor will keep a close eye on you and regularly check your progress whilst you are taking this medicine. This close monitoring will allow your doctor or physician to flag up any issues, ensure it is working properly, decide whether you are still receiving the correct dose and to ensure you should continue to receive it. A doctor will test for unwanted effects via different urine and blood tests.

With regards to the use of Acetylcysteine in children, the appropriate studies on the the effects of Acetylcysteine and the relationship of age to have not been performed in the Acetylcysteine population.


Acetylcysteine should be stored in its original container at room temperature. Make sure you always keep drugs in a safe place and out of the reach of pets and children. If you have to finish a dosage early and are left with some tablets remaining, contact your physician or local pharmacist to find out how to dispose of unused drugs in a safe way.


Whilst Acetylcysteine is a beneficial drug, it can pose a variety of potential risks to those patients who fail to communicate correctly and effectively with their physician or doctor about any current health issues or current medication they are taking in all forms. The reason the medication has been prescribed to you is because the medical professionals believe the negative aspects of the drug are outweighed by the benefits it will bring. However, in some cases, such as pregnancy, or with the possession of stomach ulcers or internal bleeding, this may not be the case. It's important therefore that you inform your doctor of all drugs you are currently taking and your past medical history. Failure to do so could see the use of Acetylcysteine impact you negatively. However, if used correctly and the correct dose is given, then Acetylcysteine is very effective in treating patients who have overdosed on paracetamol and it will help prevent liver damage.

Last Reviewed:
December 10, 2017
Last Updated:
April 04, 2018