Concept About Paracetamol – This book covers the entire syllabus of “Pharmacology” prescribed by BNMC- for a diploma in nursing science & midwifery students. We tried to accommodate the latest information and topics. This book is an examination set up according to the teachers’ lectures and examination questions.
At the end of the book, previous questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.
Concept About Paracetamol
Acetaminophen is an effective analgesic and anti-pyretic as because it is well tolerated and lacks of many of the undesired effects of aspirin. It is used as “common house-hold analgesic, It is a major active metabolite of phenacetin.
Mechanism of action of Acetaminophen
Acetaminophen inhibits PG synthesis by reversible inhibition of the enzyme cyclooxygenase mainly in the CNS (less in periphery).
Pharmacological action of Acetaminophen
- Analgesic effect (very Good)
- Anti-pyretic effect
- No anti-platelets effects
- Negligible anti-inflammatory effect
(Anti-inflammatory and anti-platelet actions action; but acetaminophen cannot inhibit the synthesis as aspirin does).
Pharmacokinetics of Acetaminophen:
a. Route of administration: Orally administered.
b. Absorption: Rapidly from the GIT.
c. Plasma half-life: 2 hours
d. Metabolism: Liver (glucoronide & sulphate conjugation)
e. Excretion: Kidney.
Dose of Paracetamol
a. Tablet: 500 mg.
b. Daily dose: 1-2 tab 4-6 hourly.
c. Max dose: 4 gm daily
d. Normal dose: 1-4 gm/day (in adult)
e. Toxic dose: 150 mg/kg or> 10 gm (in adult)
f. Fatal dose: >250 mg/kg or >20 gm (in adult)
g. Formulation: Tablet, Suspension.
Indication of Paracetamol
1. As analgesic
- Headache
- Toothache
- Arthralgia
- Myalgia
- Dysmenorrhoea
2. As anti-pyretic: For influenza.
3. Others: Acetaminophen often used instead of aspirin in order to avoid stomach irritation, allergy and in children to avoid Reye’s syndrome.
Contraindication of Paracetamol
a. Bronchial asthma
b. Severe liver damage
c. Kidney damage
Toxicities of Paracetamol
Early toxicity:
- Nausea
- Vomiting
- Anorexia
- Abdominal pain
Delayed toxicity:
- Hepatic necrosis (most serious adverse effect)
- Renal tubular necrosis
- Hypoglycaemic coma
- Pancytopenia
- Leucopenia
- Skin rash
- Urticaria
Management of acute overdose of Paracetamol
Treatment depends on the interval between overdose and presentation and on the plasma concentration of paracetamol.
1. Blood for paracetamol level should be taken immediately.
2. Gastric lavage (within 4 hours of ingestion)
3. Give antidote: acetylcysteine (IV).
4. Intravenous steroid and antihistamines to combat pseudo allergic reactions of acetyl- cysteine.
5. Monitoring of the therapy and liver damage by:
- Prothrombin time (INR)
- Serum creatinine
- Blood PH
A poor prognosis is indicated by on INR above 3, raised serum creatinine concentration or a blood PH below 7.3 recorded more than 24 hours after overdose.
If patient present >16 hours of overdose:
5. Maintain fluid and electrolytes balance.
6. maintain blood glucose level
7. Haemorrhage should be treated with fresh frozen plasma.ak
8. Haemoperfusion or liver transplantation.
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