1. Clinical Overview
Paracetamol (Acetaminophen) 150mg is a low-dose, non-opioid analgesic and antipyretic agent. It is a para-aminophenol derivative that acts centrally to inhibit prostaglandin synthesis in the brain, with minimal peripheral anti-inflammatory activity. It is a first-line agent for mild to moderate pain and fever in pediatric populations, particularly infants and young children, where precise weight-based dosing is critical. In the Indian context, this strength is primarily formulated as oral drops, suspension, or syrup for pediatric use.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 30 to 60 minutes | Approximately 4 to 6 hours | Approximately 85-98% after oral administration |
2. Mechanism of Action
The exact mechanism is not fully elucidated but is distinct from NSAIDs. It is a potent inhibitor of cyclooxygenase (COX) pathways, particularly in the central nervous system. It is believed to act on a variant of the COX enzyme, sometimes referred to as COX-3. It reduces the oxidized form of COX enzymes, preventing them from forming pro-inflammatory prostaglandins (PGs) and thromboxanes. Its primary site of action is the brain and spinal cord, where it elevates the pain threshold and acts on the hypothalamic heat-regulating center to produce antipyresis.
3. Indications & Uses
- Mild to moderate pain (e.g., headache, toothache, musculoskeletal pain) in infants and children
- Fever (pyrexia) management in pediatric patients
4. Dosage & Administration
Adult Dosage: Not indicated as a single dose. Adult therapeutic dose is 500-1000mg.
Administration: For oral drops/syrup: Use the measuring cup, dropper, or syringe provided. Shake the bottle well before use. Can be taken with or without food. Food may slightly delay absorption. Do not use a household teaspoon. Administer every 4-6 hours as needed, not exceeding 5 doses in 24 hours.
5. Side Effects
Common side effects may include:
- Nausea
- Epigastric discomfort
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin and other Coumarin Anticoagulants | Increased risk of INR elevation and bleeding, especially with chronic high-dose paracetamol use (>2g/day for several days). | Major |
| Isoniazid | Increased risk of hepatotoxicity due to induction of CYP2E1, increasing NAPQI formation. | Major |
| Enzyme Inducers (Phenobarbital, Phenytoin, Carbamazepine, Rifampicin) | Increased metabolism to NAPQI, elevating risk of hepatotoxicity even at therapeutic doses. | Major |
| Probenecid | Decreases paracetamol clearance by inhibiting glucuronidation, leading to increased plasma levels. | Moderate |
| Metoclopramide, Domperidone | Increased absorption rate of paracetamol. | Minor |
| Cholestyramine | Decreased absorption of paracetamol if taken within 1 hour. | Moderate |
| Alcohol (Chronic, excessive use) | Induces CYP2E1, increasing risk of hepatotoxicity. Also depletes glutathione stores. | Major |
| Other Hepatotoxic Drugs (e.g., Valproate, Ketoconazole, Methotrexate) | Additive risk of liver damage. | Major |
7. Patient Counselling
- DO use the measuring device provided with the medicine.
- DO adhere to the recommended dose and dosing interval (every 4-6 hours).
- DO NOT exceed 5 doses in 24 hours.
- DO NOT use with other medicines containing paracetamol (check labels of cold, cough, and flu remedies).
- DO NOT give to a child for more than 3 days for fever or 5 days for pain without consulting a doctor.
- DO NOT use in children under 2 months of age without medical advice.
8. Toxicology & Storage
Overdose: Stage 1 (0-24h): Nausea, vomiting, anorexia, malaise, pallor, diaphoresis. Stage 2 (24-72h): Apparent improvement. Right upper quadrant pain, elevated liver enzymes (AST, ALT), prolonged PT/INR. Stage 3 (72-96h): Peak hepatotoxicity: Jaundice, hepatic encephalopathy, coagulopathy, renal failure, hypoglycemia, coma. Stage 4 (4 days-2 weeks): Recovery or death from liver failure.
Storage: Store at room temperature (15-30°C), protected from light and moisture. Keep the bottle tightly closed. Do not freeze oral suspensions/syrups. Keep out of reach and sight of children. Discard any unused medicine after the expiry date.