Acetaminophen
Synonym :
Paracetamol
Mechanism :
The analgesic and antipyretic effects of paracetamol are believed to be related to the inhibition of prostaglandin synthetase (a mechanism shared by ASA and related drugs). It is postulated that the analgesic effect is produced by elevation of the pain threshold and the antipyretic effect is produced through action on the hypothalamic heat-regulating centre.
Indication :
Contraindications :
Contraindicated in known hypersensitivity to paracetamol, in hepatic and renal failure.
Dosing :
Oral or suppository: 10-15 mg/kg/per dose orally/rectally.
Neonates:
For babies born at 28-31 weeks of gestation: Every 12 hours; dose to not exceed 40 mg/kg/day.
For babies born at 32-37 weeks of gestation: Every 8 hours; dose to not exceed 60 mg/kg/day.
For term babies, 0-9 days of life: Every 6-8 hours; dose to not exceed 60 mg/kg/day.
For term babies, 10-29 days of life: Every 4-8 hours; dose to not exceed 90 mg/kg/day.
Infants:
Every 4-6 hours; dose to not exceed 75 mg/kg/day.
Children and adolescents (<60 kg):
Every 4-6 hours; dose to not exceed 1 g/dose or 75 mg/kg/day.
>12 years:
325-650 mg every 4-6 hours; dose to not exceed 3.25-4 g/day.
Adverse Effect :
Anaphylaxis. With excessive dosages it may lead to hepatic necrosis, renal tubular necrosis. Intravenous use can result in edema, hypertension, hypervolemia, hypotension, tachycardia agitation, anxiety, fatigue, headache, insomnia, hypoalbuminemia, hypokalemia, hypomagnesemia, hypophosphatemia, abdominal pain, constipation, diarrhea, nausea, vomiting, increased transaminases, infusion site pain, muscle spasms, pain in extremity, trismus, oliguria, atelectasis, breath sounds abnormal, dyspnoea, hypoxia, pleural effusion, pulmonary edema, stridor and wheezing. Use with caution in patients with G6PD deficiency.
Interaction :
Warfarin: Prolonged, regular use may prolong prothrombin time.
Metoclopramide and domperidone: Enhance absorption of paracetamol.
Cholestyramine: Reduces absorption of paracetamol.
Zidovudine: Increased risk of neutropenia.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function |
| 10-20 | Dose as in normal renal function |
| <10 | 500 mg – 1 g every 6–8 hours |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Dialysed. Dose as in GFR<10 mL/ min |
| HDF/High flux | Dialysed. Dose as in GFR<10 mL/ min |
| CAV/VVHD | Unknown dialysability. Dose as in normal renal function |
Hepatic Dose :
Use with caution in patients with severe hepatic impairment.