N-Acetyl-Cysteine
Chemical
Synthetic N-acetyl derivative of endogenous a-acid L-cysteine
Use (in ICU)
- Antioxidant
- Paracetamol overdose
- Irrespective of P level (staggered OD)
- Doubt over time of P OD (despite level)
- Paracetamol level > 100mg/L at 4hrs and 15mg/L at 15h
- Prophylaxis of radiocontrast induced kidney injury
- Acute and chronic bronchopulmonary disease
Presentation
Clear colourless solution for infusion
200mg/ml injection
Dose
Paracetamol OD:
- Initial loading 150mg/kg in 200ml infused over 1hr
- 50mg/kg in 500ml over next 4hrs
- 100mg/kg in 1L over next 16hrs
- Receiving 300mg/kg over 21hrs
Route
IV
Inhaled for mucolysis
DoA
t1/2b 5.6 hrs after IV dose
MoA
Reduces hepatic toxicity of NAPQI;
- NAC acts as precursor for the synthesis of antioxidant enzyme glutathione, replenishing stores to inactivate NAPQI
- Reduces oxidised thiol groups of Paracetamol’s reactive metabolite
Glutathione reduces disulfide bonds in mucoproteins, resulting in liquification of mucus
Antioxidant effects via reduction in free radicals
PK
A
Rapidly absorbed but low OBA 10-30%
M
Rapid. Hepatic. Deacetylated by liver to cysteine and subsequently metabolised
E
30% unchanged in urine
Adverse Effects
CNS: fever
CVS: chest tightness, hypotension, HTN, tachycardia
GI: N+V
ENT: rhinorrhea
Clamminess