Acetylcysteine Macure

What Is Acetylcysteine Macure and What Is It Used For?

Quick Answer: Acetylcysteine Macure is a 200 mg/ml intravenous solution of N-acetylcysteine (NAC) used primarily as the antidote for paracetamol (acetaminophen) poisoning. It protects the liver from the toxic effects of paracetamol metabolites by replenishing the body's glutathione reserves.

Acetylcysteine Macure belongs to a class of medications known as antidotes and mucolytic agents. As a concentrated solution designed for intravenous (IV) infusion, it is formulated specifically for hospital use in the management of acute paracetamol (acetaminophen) overdose — one of the most common forms of drug poisoning worldwide. According to the World Health Organization, paracetamol overdose is the leading cause of acute liver failure in many Western countries, and acetylcysteine is the only established antidote.

The primary mechanism of action in paracetamol poisoning involves the role of acetylcysteine as a precursor to glutathione, the body’s most important intracellular antioxidant. Under normal circumstances, a small fraction of paracetamol is metabolized by the cytochrome P450 enzyme system in the liver into a highly reactive intermediate called N-acetyl-p-benzoquinone imine (NAPQI). At therapeutic doses, NAPQI is rapidly detoxified by conjugation with glutathione. However, in overdose situations, glutathione stores become depleted, and excess NAPQI binds covalently to hepatocellular proteins, triggering oxidative stress, mitochondrial dysfunction, and ultimately liver cell necrosis.

Acetylcysteine intervenes at multiple points in this toxic cascade. By providing cysteine — the rate-limiting amino acid for glutathione synthesis — it restores hepatic glutathione reserves, enabling continued NAPQI detoxification. Additionally, acetylcysteine has direct antioxidant properties through its free sulfhydryl (thiol) group, which can scavenge free radicals and reactive oxygen species. There is also evidence that acetylcysteine improves hepatic microcirculation and oxygen delivery, which may contribute to its protective effect even in patients who present late after overdose.

The clinical importance of intravenous acetylcysteine cannot be overstated. Large observational studies and decades of clinical experience have demonstrated that timely administration of acetylcysteine virtually eliminates the risk of death from paracetamol hepatotoxicity when given within 8 hours of ingestion. Even when treatment is initiated later, it significantly reduces the severity of liver injury and improves survival. The medication is listed on the WHO Model List of Essential Medicines and is recommended by all major toxicology and emergency medicine guidelines worldwide, including those from the National Institute for Health and Care Excellence (NICE), the American College of Medical Toxicology (ACMT), and the European Association for the Study of the Liver (EASL).

Beyond its use in paracetamol overdose, intravenous acetylcysteine has been investigated in a range of other clinical contexts. These include the prevention of contrast-induced nephropathy in patients undergoing radiological procedures, the management of non-paracetamol-related acute liver failure, and as a mucolytic agent administered by nebulization for patients with thick, tenacious bronchial secretions. However, the evidence base for these off-label applications varies, and the primary approved indication for Acetylcysteine Macure 200 mg/ml solution remains the treatment of paracetamol poisoning.

What Should You Know Before Receiving Acetylcysteine Macure?

Quick Answer: In the context of paracetamol overdose, the benefit of acetylcysteine almost always outweighs the risks and treatment should not be delayed. However, patients with a history of asthma, anaphylaxis, or significant allergic conditions should be closely monitored during infusion, as anaphylactoid reactions are more common in these groups.

Contraindications

The only absolute contraindication to intravenous acetylcysteine is known, confirmed anaphylaxis (immune-mediated allergic reaction) to acetylcysteine itself. It is important to distinguish true anaphylaxis from the much more common anaphylactoid reactions that occur during infusion; the latter are dose-rate dependent, non-immune mediated, and manageable with infusion rate adjustment and supportive treatment.

In practice, even in patients with a documented history of anaphylactoid reactions to previous acetylcysteine treatment, the medication is still administered when clinically indicated for paracetamol overdose, because the risk of untreated paracetamol hepatotoxicity far exceeds the risk of the infusion reaction. In such cases, pretreatment with antihistamines and careful infusion rate management are employed under close medical supervision.

Warnings and Precautions

Several important precautions must be observed when administering Acetylcysteine Macure. These are primarily relevant to the clinical team managing the patient, but understanding them is valuable for patients and caregivers:

• Asthma and bronchospasm: Patients with asthma or a history of bronchospasm are at increased risk of experiencing respiratory complications during the infusion. Bronchospasm can occur as part of an anaphylactoid reaction, particularly during the initial loading dose. Healthcare teams should have bronchodilator therapy (such as salbutamol) readily available and should monitor respiratory status closely throughout treatment.
• Anaphylactoid reactions: Non-immune-mediated anaphylactoid reactions are the most common adverse effect of IV acetylcysteine and typically present during the first infusion bag. Symptoms range from mild (flushing, itching, nausea) to severe (bronchospasm, hypotension, angioedema). The incidence is dose-rate dependent — slower infusion rates substantially reduce the risk. Clinical protocols may include a modified, slower initial infusion (over 60 minutes instead of 15 minutes) to mitigate this.
• Fluid and electrolyte balance: The standard three-bag IV acetylcysteine protocol involves administration of significant fluid volumes (typically using 5% glucose as the diluent). In patients with restricted fluid tolerance — such as those with heart failure, renal impairment, or in pediatric patients where fluid overload is a concern — modified protocols using reduced diluent volumes are recommended.
• Weight-based dosing: All doses must be accurately calculated based on the patient’s actual body weight. Dosing errors are a recognized risk with the traditional three-bag protocol due to its complexity. For patients weighing more than 110 kg, doses should be capped at the 110 kg level to avoid excessive dosing. Hospital pharmacists and clinical toxicologists play a key role in ensuring dose accuracy.
• Hepatic impairment: No dose adjustment is required for patients with pre-existing liver disease. In fact, patients with chronic liver disease who take a paracetamol overdose may be at increased risk of hepatotoxicity and should receive acetylcysteine promptly.

Pregnancy and Breastfeeding

In the setting of paracetamol overdose, acetylcysteine should be administered regardless of pregnancy status. The risk of untreated paracetamol poisoning to both the mother and the developing fetus substantially outweighs any theoretical risk from the antidote. Paracetamol crosses the placenta, and fetal hepatotoxicity has been documented in cases of maternal overdose. Acetylcysteine also crosses the placenta and may provide direct hepatoprotective benefit to the fetal liver.

There are no adequately controlled studies of intravenous acetylcysteine in pregnant women specifically, but decades of clinical experience have not identified any specific fetal harm attributable to the antidote. Major clinical toxicology guidelines, including those from NICE and the American College of Medical Toxicology, explicitly recommend that treatment should not be withheld or delayed due to pregnancy. The treating physician should inform the patient about the necessity of treatment and coordinate care with obstetric specialists as appropriate.

Regarding breastfeeding, it is not known whether intravenous acetylcysteine passes into breast milk in clinically significant amounts. Given the short treatment duration (approximately 21 hours) and the clinical context of acute poisoning management, the decision to continue breastfeeding should be made in consultation with the treating physician.

Interference with Laboratory Tests

Acetylcysteine can interfere with certain laboratory assays, which is an important consideration during clinical management. Notably, it may cause falsely low readings on some colorimetric paracetamol assays, potentially leading to underestimation of serum paracetamol levels. It can also interfere with INR (International Normalized Ratio) measurements, producing falsely elevated results. Clinical teams should be aware of these potential interferences and interpret laboratory values in the context of the clinical picture.

How Does Acetylcysteine Macure Interact with Other Drugs?

Quick Answer: Clinically significant drug interactions with IV acetylcysteine are limited. It may enhance the vasodilatory effects of nitroglycerin and should not be mixed with other drugs in the same infusion line. Activated charcoal reduces oral but not IV acetylcysteine absorption. In emergency overdose treatment, interactions rarely alter the decision to treat.

Drug interactions with intravenous acetylcysteine are relatively few, and in the acute setting of paracetamol poisoning, the imperative to treat generally overrides concerns about potential interactions. Nonetheless, healthcare professionals should be aware of the following documented or theoretically significant interactions.

Clinically Significant Interactions

Pharmaceutical Incompatibilities

Acetylcysteine Macure solution must not be mixed with other medications in the same infusion bag or syringe. The solution is incompatible with rubber and certain metals, and contact with these materials should be avoided during preparation. When co-administration of other intravenous medications is necessary, they should be given through a separate intravenous line or sequentially after flushing the line.

The recommended diluents for Acetylcysteine Macure are glucose 5% (dextrose 5%) and sodium chloride 0.9% (normal saline). Glucose 5% is generally preferred as the standard diluent. The diluted solution should be used within 24 hours when stored at room temperature.

In the context of paracetamol overdose management, patients may also receive other treatments such as ondansetron (for nausea and vomiting associated with acetylcysteine infusion), antihistamines (for anaphylactoid reactions), or bronchodilators (for bronchospasm). These medications are given through separate routes or lines and do not have clinically significant pharmacological interactions with acetylcysteine.

What Is the Correct Dosage of Acetylcysteine Macure?

Quick Answer: Acetylcysteine Macure is administered intravenously in a three-stage protocol over approximately 21 hours. The dose is calculated based on body weight (capped at 110 kg). The standard protocol delivers a total dose of 300 mg/kg: a 150 mg/kg loading dose, followed by 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours.

The dosage of intravenous acetylcysteine for paracetamol overdose is strictly weight-based and must be calculated and administered by trained healthcare professionals in a hospital setting. Dosing protocols have been refined over decades to balance efficacy against the risk of anaphylactoid reactions. The traditional three-bag protocol, first developed by Prescott and colleagues, remains the standard approach used in most countries.

Standard Three-Bag Protocol (Adults)

The total dose delivered across all three infusion bags is 300 mg/kg over approximately 21 hours. For patients weighing more than 110 kg, doses are calculated using 110 kg as the maximum weight to prevent excessive dosing. Fluid volumes may also need adjustment in patients with fluid restrictions.

Children and Adolescents

The same weight-based dosing protocol applies to children as to adults, but with critical adjustments to diluent volumes to prevent fluid overload and hyponatremia. Reduced-volume protocols have been developed specifically for pediatric patients. Children weighing less than 20 kg require particularly careful fluid volume calculations, and treatment should ideally be managed in a pediatric emergency department or with input from a pediatric toxicologist.

The British National Formulary for Children (BNFC) provides specific pediatric fluid volume guidelines that differ from adult protocols. Healthcare providers should consult the most current local or national pediatric poisoning guidelines when treating children with paracetamol overdose.

Elderly Patients

No dose adjustment based solely on age is required for elderly patients. However, elderly patients may be at increased risk of fluid overload due to reduced cardiac reserve and renal function. They may also be taking multiple medications that could interact with acetylcysteine or complicate the clinical picture. Close monitoring of fluid balance, renal function, and hemodynamic parameters is advisable throughout treatment.

Treatment Continuation and Assessment

Unlike oral medications, the concept of a “missed dose” does not apply to intravenous acetylcysteine in the same way. If the infusion is interrupted (for example, due to an anaphylactoid reaction), the clinical team will assess whether to restart the infusion at a slower rate or to manage the reaction and then resume treatment. At the end of the standard 21-hour protocol, blood tests (including liver function, INR, creatinine, and serum paracetamol level) are performed to determine whether the patient requires continued treatment with an extended acetylcysteine infusion.

Overdose of Acetylcysteine

What Are the Side Effects of Acetylcysteine Macure?

Quick Answer: The most common side effects are anaphylactoid reactions during the initial infusion, including nausea, vomiting, flushing, itching, and rash. These are dose-rate dependent and usually manageable by temporarily stopping or slowing the infusion. Serious reactions such as bronchospasm or severe hypotension are less common but require immediate treatment.

Adverse reactions to intravenous acetylcysteine are well characterized and primarily related to non-immune-mediated histamine release (anaphylactoid reactions). Unlike true allergic (anaphylactic) reactions, these are dose-rate dependent rather than immune-mediated, meaning they are influenced by the speed of infusion rather than by prior sensitization. The overall incidence of any anaphylactoid reaction during IV acetylcysteine treatment is estimated at 10–20% with the traditional 15-minute initial infusion, but decreases to approximately 5–10% when the loading dose is infused over 60 minutes.

The majority of anaphylactoid reactions to IV acetylcysteine are mild to moderate in severity and resolve either spontaneously upon temporary cessation of the infusion or with simple interventions such as antihistamines (e.g., chlorphenamine or cetirizine) and anti-emetics (e.g., ondansetron). Studies have consistently demonstrated that slowing the initial loading dose infusion from 15 minutes to 60 minutes significantly reduces the rate and severity of these reactions without compromising hepatoprotective efficacy.

Risk factors for more severe anaphylactoid reactions include pre-existing asthma, a history of atopic conditions, lower serum paracetamol levels at presentation (paradoxically, patients with lower paracetamol levels appear more susceptible), and faster infusion rates. Clinical teams should be prepared to manage bronchospasm with inhaled bronchodilators and to treat hypotension with intravenous fluids and, if necessary, vasopressors.

It is important to emphasize that anaphylactoid reactions to acetylcysteine, while common and sometimes distressing, are rarely life-threatening and should not deter clinicians from administering the antidote when indicated. The morbidity and mortality associated with untreated paracetamol hepatotoxicity far exceed the risks associated with acetylcysteine adverse effects.

Reporting Side Effects

Healthcare professionals should report any suspected adverse reactions through their national pharmacovigilance reporting system. In the United Kingdom, this is the Yellow Card Scheme operated by the MHRA. In the European Union, reports can be submitted through the national competent authority. Continued surveillance helps refine our understanding of the safety profile of intravenous acetylcysteine.

How Should You Store Acetylcysteine Macure?

Quick Answer: Store unopened ampoules at or below 25°C. Do not freeze. Protect from light. Once diluted, the solution should be used within 24 hours if stored at room temperature. This is a hospital-managed medication — storage is handled by pharmacy departments.

Acetylcysteine Macure 200 mg/ml solution for infusion is supplied in glass ampoules and is stored and managed by hospital pharmacy departments under controlled conditions. Proper storage is essential to maintain the chemical stability and sterility of the product:

• Unopened ampoules: Store at or below 25°C (77°F). Do not refrigerate or freeze. Keep the ampoules in the outer carton to protect from light.
• Diluted solution: Once diluted in glucose 5% or sodium chloride 0.9%, the solution should be used within 24 hours when stored at room temperature (15–25°C). Chemical and physical in-use stability has been demonstrated for 24 hours at 25°C.
• Visual inspection: Before use, the solution should be visually inspected for particulate matter and discoloration. The solution is normally clear and colorless to slightly yellow or pink-purple. A color change to light purple does not indicate loss of potency. However, solutions that are deeply colored, turbid, or contain visible particulate matter should not be used.

As a hospital-only medication, patients do not need to concern themselves with storage conditions. The hospital pharmacy is responsible for ensuring that stock is stored correctly, within its expiry date, and that diluted solutions are prepared aseptically and used within the recommended timeframe.

Unused or expired medication should be disposed of in accordance with hospital pharmaceutical waste procedures and local environmental regulations. Acetylcysteine solution should not be poured down drains or disposed of as general waste.

What Does Acetylcysteine Macure Contain?

Quick Answer: Each milliliter of Acetylcysteine Macure contains 200 mg of acetylcysteine as the active ingredient. The solution also contains disodium edetate (EDTA) as a stabilizer, sodium hydroxide for pH adjustment, and water for injections. It is a preservative-free sterile solution.

Understanding the full composition of Acetylcysteine Macure is important for healthcare professionals preparing the infusion, particularly to identify potential incompatibilities and to advise patients with known allergies or sensitivities to specific excipients.

Active Substance

The active pharmaceutical ingredient is acetylcysteine (N-acetyl-L-cysteine), present at a concentration of 200 mg per milliliter. This highly concentrated formulation allows for the delivery of the large doses required for paracetamol overdose treatment while minimizing the volume of undiluted solution needed. Acetylcysteine is a white, crystalline powder in its pure form, and when dissolved, produces a clear, colorless to slightly colored solution.

Inactive Ingredients (Excipients)

The excipients in Acetylcysteine Macure are minimal, reflecting the parenteral (intravenous) route of administration and the need for a sterile, preservative-free formulation:

• Disodium edetate (EDTA) — a chelating agent used as a stabilizer to prevent oxidation of the active substance and maintain solution clarity. EDTA binds trace metals that could catalyze degradation reactions.
• Sodium hydroxide — used to adjust the pH of the solution to the appropriate range for intravenous administration (typically pH 6.0–7.5).
• Water for injections — the pharmaceutical-grade solvent, meeting strict purity standards for parenteral use.

Ampoule Presentation

Acetylcysteine Macure is available in glass ampoules, typically containing 10 mL of solution (equivalent to 2,000 mg of acetylcysteine per ampoule). The number of ampoules required for a complete treatment course depends on the patient’s body weight. For a 70 kg adult, the total dose is 21,000 mg (300 mg/kg × 70 kg), requiring approximately 10.5 ampoules of 10 mL. Hospital pharmacies should ensure adequate stock is maintained, as treatment initiation should not be delayed due to supply issues.