Paracetamol  is a commonly prescribed drug in Medical practice. It is rapidly absorbed on oral intake and metabolized to sulph and glucoronide  group. Small amount is excreted in Urine.

Poisoning

Mechanism Of Toxiciy:

• Paracetamol  is Metabolised to NABQI ( N- Acetyl –p-BenzoQuinimine) . Glutathione detoxifies it into Mercatopuric acid which is excreted in urine.
• At Toxic Level, when >70 % of Glutathione is depleted , NABQI combines with Hepatic Macromolecules  causing hepatocellular damage.

Metabolism

Clinical Features:

1. Stage I ( within 24 hours) : Anorexia, Nausea/vomiting, malaise,pallor,diaphoresis.
2. Stage II ( 24-48 hours):  Resolution of symptoms of stage I. Rt. Upper quadrant pain, Deranged LFT, Oliguria, tachycardia, hypotension.
3. Stage III (72-96 hours) : LFT abnormal peak, coagulopathy, hepatic encephalopathy, renal failure.
4. Stage IV (4 days-2 weeks ) : Resolution of hepatic dysfunction, resolution of organ failure.

Laboratory investigations :

1. Serum Transaminase levels : ALT and AST raised at 24 hours, peak at 72 hours

Serum ALT/AST more than 1000IU/L- toxicity defined.

1. Serum Glucose, PT and Bilirubin, hepatic enzymes.
2. Electrolyte, KFT, Lactate.
3. Urine analysis for proteinuria and hematuria – ATN.
4. ABG.

Prognostic Factors :

• pH, Serum Creatinine, PT, Lactate.
• Toxic Dose – 200mg/kg in children or 7.5 gm at once in adolescents.

Differential Diagnosis :

1. Reye’s syndrome
2. Infective Hepatitis

Treatment:

1. Small amount ingestion needs only observation.

Else :

1. Gastric Lavage
2. Activated Charcoal
3. Serial measurements of LFT, PT, Creatinine
4. Specific Antidote :  N-acetyl cysteine(NAC), which is a precursor for glutathione synthesis.

140mg/kg Loading dose, then 70mg/kg 4 hourly for 3 days.

Methionine can also be used.

( Compiled For Use by Medical personal and Students only, Do not  use drug without Prescription)

By : Dr. Merry Shrestha

NMCTH.