N-Acetylcysteine Indications

Acetylcysteine
200 mg/ml solution in a 10 ml ampoule (20 % solution)

N-Acetylcysteine (NAC) is used in overdose/ poisoning of paracetamol. After it is administered, it undergoes absorption and is later metabolised to cysteine (direct precursor in the synthesis of hepatic intracellular glutathione).

The paracetamol poisoning causes oxidative stress and inflammation which consequently causes a depletion in the glutathione (anti-oxidant) reserves.

 NAC is most beneficial if administered within 8 hours of ingestion. after that, its benefits decline. 

In accordance with National Poison Information Service (NPIS), previous anaphylactoid reactions to NAC is not an absolute contraindication. The latter can be pre-treated with anti-histamines: IV Chlorpheniramine 10 mg. 

Treatment of Paracetamol Poisoning via IV:

1. 150 mg/kg given in 200 ml of infusion fluid over 15 minutes.
2. 50 mg/kg in 500 ml infusion fluid over the next 4 hours.
3. 100 mg/kg in 1 L infusion over the next 16 hours.

The prepared infusion should be clear, colourless and free from any particulate matter and discolouration before administration. 

Table 1: Properties of NAC

Technical information
Incompatible with	Rubber and metals
Compatible with	Plastic, glass, stainless steel Flush: NaCL 0.9 % Solutions: Glucose 5 % (preferable), NaCL 0.9 % *Solutions should include additional KCL.
pH	6.0 – 7.5
Storage	Below 250C Any changes in color of solution to that of light purple is not significant. May still be used.
Stability	Prepared solutions should be used immediately if possible; otherwise may be kept for 24 h
Monitoring Parameters
Measures	Rationale
Liver Function & INR	Increased transaminases: hepatotoxicity. NAC may increase INR. INR ≤ 1.3, normal transaminases: discontinue treatment. Transaminases & INR raised: repeat third infusion over 16 h.
ECG	May be changes
Renal function & Serum K	Renal failure may be present as a complication. Low K+ may be present.
Sodium Bicarbonate	To avoid metabolic acidosis complications.
Other Information
Infusion	Rapid infusions may facilitate higher chances of hypersensitivity reactions.	KIV antihistamines and corticosteroids.
Overdose	Anaphylactoid reactions, Hepatic encephalopathy	KIV vitals

Treating patients under restriction of fluid (ROF):

Range of dilutions in 100 - 250 ml of Glucose 5 % .
Some centres used undiluted infusions (10 g in 50 ml).
Use central line for undiluted solutions.

References:
1. http://www.pharmpress.com/files/docs/Injectable%20Drugs%20sample.pdf
2. http://www.ukcpa.org.uk/ukcpadocuments/9.pdf