N-Acetyl-L-Cysteine vs. N-Acetylcysteine

What's the Difference?

N-Acetyl-L-Cysteine (NAC) and N-Acetylcysteine (NAC) are two forms of the same compound, with the former being the more specific and precise name. Both NAC and N-Acetyl-L-Cysteine are derivatives of the amino acid cysteine and are commonly used as dietary supplements. They are known for their antioxidant properties and ability to support liver health. NAC is often used as a mucolytic agent to help break down and thin mucus, making it useful in treating respiratory conditions. Overall, N-Acetyl-L-Cysteine and N-Acetylcysteine are essentially the same compound, with the former being the more scientifically accurate name.


Chemical FormulaC7H13NO3SC5H9NO3S
Molecular Weight163.19 g/mol163.19 g/mol
SynonymsNAC, N-Acetyl CysteineNAC, N-Acetyl Cysteine
StructureN-Acetyl-L-Cysteine StructureN-Acetylcysteine Structure
UsesTreatment of acetaminophen overdose, antioxidant, mucolytic agentTreatment of acetaminophen overdose, antioxidant, mucolytic agent
SolubilitySoluble in waterSoluble in water

Further Detail


N-Acetyl-L-Cysteine (NAC) and N-Acetylcysteine (NAC) are two forms of the same compound that have gained significant attention in the field of medicine and health. Both NAC and NAC are derivatives of the amino acid cysteine and are known for their antioxidant properties. However, despite their similar names and functions, there are subtle differences between the two compounds that are worth exploring. In this article, we will delve into the attributes of N-Acetyl-L-Cysteine and N-Acetylcysteine, highlighting their similarities and differences.

Chemical Structure

Both N-Acetyl-L-Cysteine and N-Acetylcysteine share a common chemical structure, with an acetyl group attached to the cysteine molecule. This acetyl group is responsible for enhancing the stability and bioavailability of the compound. However, the key difference lies in the stereochemistry of the acetyl group. N-Acetyl-L-Cysteine has an L-configuration, indicating that the acetyl group is attached to the left side of the cysteine molecule. On the other hand, N-Acetylcysteine lacks stereochemistry and does not specify the configuration of the acetyl group. This subtle difference in stereochemistry may have implications for the compound's biological activity and pharmacokinetics.

Medical Uses

Both N-Acetyl-L-Cysteine and N-Acetylcysteine have been extensively studied for their therapeutic potential in various medical conditions. One of the most well-known applications of these compounds is their use as mucolytic agents. They help to break down and thin mucus, making it easier to clear from the respiratory tract. This property has made them valuable in the treatment of respiratory conditions such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, and bronchitis.

Furthermore, N-Acetyl-L-Cysteine and N-Acetylcysteine have shown promise in the management of acetaminophen (paracetamol) overdose. They act as precursors for glutathione, a potent antioxidant that plays a crucial role in detoxifying the toxic metabolites of acetaminophen. By replenishing glutathione levels, these compounds help protect the liver from the damaging effects of acetaminophen overdose.

In addition to their mucolytic and hepatoprotective properties, N-Acetyl-L-Cysteine and N-Acetylcysteine have also been investigated for their potential in psychiatric disorders. Studies have suggested that these compounds may have a role in the management of conditions such as bipolar disorder, obsessive-compulsive disorder (OCD), and addiction. They are believed to modulate glutamate levels in the brain, which can have a positive impact on mood and behavior.

Moreover, N-Acetyl-L-Cysteine has been explored for its potential in the treatment of neurodegenerative diseases such as Alzheimer's and Parkinson's. It has been shown to possess neuroprotective properties, reducing oxidative stress and inflammation in the brain. These effects may help slow down the progression of these debilitating conditions.


When it comes to pharmacokinetics, N-Acetyl-L-Cysteine and N-Acetylcysteine exhibit some differences. N-Acetyl-L-Cysteine is known for its rapid absorption and bioavailability, making it an effective therapeutic agent. It is readily converted into cysteine, which serves as a precursor for glutathione synthesis. On the other hand, N-Acetylcysteine has a slower absorption rate and lower bioavailability compared to N-Acetyl-L-Cysteine. This may be attributed to the absence of stereochemistry, which could affect the compound's interaction with enzymes and transporters involved in its absorption and metabolism.

Safety and Side Effects

Both N-Acetyl-L-Cysteine and N-Acetylcysteine are generally considered safe when used as directed. However, like any medication or supplement, they may cause side effects in some individuals. Common side effects include gastrointestinal symptoms such as nausea, vomiting, and diarrhea. These side effects are usually mild and transient.

In rare cases, allergic reactions may occur, characterized by symptoms such as rash, itching, and swelling. If any severe allergic reactions or adverse effects are experienced, medical attention should be sought immediately.

It is worth noting that N-Acetyl-L-Cysteine has been studied more extensively than N-Acetylcysteine, and its safety profile is better established. This is partly due to the fact that N-Acetyl-L-Cysteine has been approved as a prescription medication in some countries, while N-Acetylcysteine is more commonly available as an over-the-counter supplement.


In conclusion, N-Acetyl-L-Cysteine and N-Acetylcysteine are two closely related compounds that share many similarities in terms of their chemical structure and medical uses. Both compounds have demonstrated efficacy as mucolytic agents and in the management of acetaminophen overdose. They have also shown potential in the treatment of psychiatric disorders and neurodegenerative diseases.

While N-Acetyl-L-Cysteine and N-Acetylcysteine have similar functions, their stereochemistry and pharmacokinetics differ. N-Acetyl-L-Cysteine has an L-configuration and exhibits better absorption and bioavailability compared to N-Acetylcysteine. However, both compounds are generally safe when used as directed, with mild and transient side effects.

Further research is needed to fully understand the similarities and differences between N-Acetyl-L-Cysteine and N-Acetylcysteine, as well as their potential applications in various medical conditions. As with any medication or supplement, it is important to consult with a healthcare professional before starting any new treatment regimen.

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