L5: Paracetamol Flashcards
Origin of Paracetamol
- Synthetic non opiate derivative of p-amino phenol (N-acetyl-p-amino phenol NAPAP) or (Acetaminophen)
uses of Paracetamol
- Analgesic & anti pyretic properties but with no or weak anti-inflammatory criteria.
what is a major metabollite for acetanilide & Phenacetin?
Paracetamol?
(causes Met HB)
Preparations of Paracetamol
Toxic action of Paracetamol in therapeutic doses
Toxic action of Paracetamol in toxic overdoses
Manner of poisoning by Paracetamol
- Accidental in children
- Suicidal (very common)
- Never homicidal
what are substances that delay gastric emptying?
- anticholinergics
- Antihistamines
- Anti depressants
- Antipsychotics
- Antiparkinsonian
- Anticonvulsants
Absorbtion of Paracetamol
- Rapidly absorbed,
- But may delay in cases of SR Proparation, by Other drugs and high carbohydrate foods
Distribution of Paracetamol
Metabolism of Paracetamol
95% metabolized by the liver.
excretion of Paracetamol
5% excreted unchanged in the kidney.
what is the toxic dose of Paracetamol?
CP of Paracetamol toxicity
- Stage I (0-24 hours): “GIT upset stage”
- Stage Il: (1-2 Days): “Asymptomatic Stage”
- Stage III: (3-5 days): “Hepatic Stage”
- Stage IV: (5 days - 2 weeks): “Recovery Stage”
Stage II of Paracetamol toxicity
Stage 1 of Paracetamol toxicity
- Anorexia, nausea, vomiting, pallor & malaise.
- Symptoms subside and the patient may appear normal
Stage III of Paracetamol toxicity
Stage IV of Paracetamol toxicity
- Normalization of the liver function tests begins about 8 days post-ingestion
- Hepatic architecture returns to normal within 3 months.
Investigations for Paracetamol toxicity
- Plasma Acetaminophen Level
- Liver function tests
- Renal Functions Tests
plasma acetaminophen level in Paracetamol toxicity
Liver Function tests in Paracetamol toxicity
Renal Function Tests in Paracetamol toxicity
In cases of Evidence of renal damage “Proteinuria, Phosphaturia”.
TTT aspects of Paracetamol toxicity
- Emergency and supportive measures
- Decontamination
- Antidote
- Enhanced Elimination
Emergency & Supportive TTT of Paracetamol toxicity
- Treatment of Shock, Hypotension & Arrhythmia.
Decontamination of Paracetamol toxicity
- Gastric Lavage
- Activated Charcoal
Gastric Lavage in Paracetamol toxicity
- If large ingestion of paracetamol & presented within 1 hour
- Or in concomitant ingestion of drugs which delay Gl absorption.
Activated Charcoal in Paracetamol toxicity
If <4 hours from ingestion:
- Administer as a single dose 1g/kg orally or nasogastric tube.
- Does not advorsely affoct oral N-acetylcystein (NAC) efficacy.
Antidote in Paracetamol toxicity
N-Acetylcystein 20%
Indications of N-Acetylcystein 20% in Paracetamol toxicity
- The first choice, it is best given within 8 hours.
- Indicated for toxic levels of paracetamol.
- Do not delay antidote therapy for lack of a paracetamol level.
Mechanism of NAC
- Increase synthesis of glutathione.
- Increase conversion to sulfate metabolite.
- Decrease conversion to toxic intermediates.
oral doses of N-Acetylcystein in Paracetamol toxicity
IV infusion of N-Acetylcystein in Paracetamol toxicity
SE of oral antidote in Paracetamol toxicity
- Nausea, vomiting &diarrhea.
- Extremely offensive sulfur odor.
SE of IV infusion of antidote in Paracetamol toxicity
- Infravenous anaphylactoid reaction (treaf with
ontihistamines, epinephrine). - Isolated effects include
1. Flushing
2. Pruritus
3. Angioedema
4. Bronchospasm
5. Tachycardia
6. Hypotension.
Enhanced Elimination in Paracetamol toxicity
Hemedialysis & Hemoperlusion
Iodicated in selested patisot with:
* Plasma level > 1000 microgram/ml
* Hypersensitivity to NAC
* Renal failure > 48 h
Supportive therapy for liver in Paracetamol toxicity
what are groups at high risk of Paracetamol toxicity?
