- It inhibits prostaglandin synthesis in the CNS by inactivating cyclooxygenase and hence explains antipyretic and analgesic effects (not peripherally).
Membrane phospholipids
↓ Phospholipase A
Arachidonic acid
Cyx. ↓x ↓Lipoxygenase
Prostaglandins Leukotrienes
Adverse effects (ADR):
1. Hepatotoxicity or hepatic necrosis
2. Nausea, dizziness, excitement, disorientation, rashes, leukoplakia @NiD2ER
Use:
1. As antipyretic drug (to treat fever)
2. As analgesic drug (to treat pain)
Contraindications:
1. Chronic alcoholics or severe hepatic impairment
2. Premature babies (<2 years)
Note:
1. Acute paracetamol poisoning:
- Due to overdose of paracetamol (fetal dose = 250 mg/kg)
Mechanism:
Paracetamol → From inactive metabolites → Normally excreted
Cyt. 450 ↓
NAPQI (highly toxic metabolite) → Normally excreted
↓
Covalently bind with sulfhydryl group
↓
Liver/ Kidney damage
2. Specific antidote for paracetamol poisoning: N-acetylcysteine
