tylenol Flashcards
acetaminophen
Acetaminophen (paracetamol, N-acetyl-p-aminophenol or APAP) - over-the-counter preparations alone or in combination with multiple medications
One of the most common agents in overdose reported - American Association of Poison Control Centers.
APAP toxicity - most common cause of hepatic failure requiring liver transplantation in the United States and Great Britain.
Mortality/Morbidity: The majority of patients with APAP overdose survive with supportive care in conjunction with antidotal therapy.
If correctly treated in a timely manner, most patients do not suffer significant sequelae.
half life
2-3 hours
Acute ingestion
TOXIC - Acute ingestion of APAP > 7.5 gm in adults or 150 mg/kg in children
what can it do in excess
Excess of this metabolite - covalently bind with hepatocytes vital proteins and the lipid bilayer - centrilobular hepatic necrosis.
The at-risk dose may be lower in persons with alcoholism and other susceptible individuals.
what is the clinical of the poisoning- the steps
Phase 1: Pallor/Malaise/Vomiting/Diaphoresis
Phase 2: Right upper quadrant abdominal tenderness/Tachycardia/Hypotension possibly due to volume loss
Phase 3: Tender hepatic edge/ Jaundice/ Evidence of coagulopathy, including gastrointestinal (GI) bleeding/ Evidence of hepatic encephalopathy
Phase 4: Resolution
phase 1
Phase 1 (0-24 h): Asymptomatic/Anorexia/Nausea and vomiting/Diaphoresis/Malaise
phase 2
Phase 2 (18-72 h):Decreasing symptoms of phase 1/Right upper quadrant abdominal pain and rising liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST])
phase 3
Phase 3 (72-96 h):Centrilobular hepatic necrosis with accompanying abdominal pain/ Jaundice/ Coagulopathy/Hepatic encephalopathy/Recurrence of nausea and vomiting/Renal failure/Fatality
phase 4
Phase 4 (4 d to 3 wk):Complete resolution of symptoms/Complete resolution of organ failure
N-acetylcysteine (NAC)
The antidote for APAP poisoning is N-acetylcysteine (NAC).
NAC is theorized to work by a number of protective mechanisms.
Early after overdose, NAC prevents the formation and accumulation of NAPQI.
N-acetylcysteine (NAC)- Mechanism of Action
NAC increases glutathione stores, combines directly with NAPQI as a glutathione substitute, and enhances sulfate conjugation.
NAC also functions as an anti-inflammatory and antioxidant and has positive inotropic and vasodilating effects, which improve microcirculatory blood flow and oxygen delivery to tissues.
NAC is most effective when administered within 8 hours of ingestion.
When indicated, however, NAC should be administered regardless of time since the overdose
Transaminase levels- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT)
begin to rise within 24 hours post-ingestion
peak at 48-72 hours.
Severe toxicity can be defined as AST or ALT greater than 1000 IU/L.
Measures of hepatic function Serum glucose Prothrombin time (PT) and bilirubin
Electrolytes and Creatinine
anion gap acidosis - help rule out co-ingestion, metabolic disorder from vomiting, or liver failure (if subacute ingestion)
Renal - coexist with or, rarely, be independent of liver toxicity in overdose
more likely to occur in alcoholics
not observed acutely but rather within 2-3 days of overdose.
Human chorionic gonadotropin (HCG)
Human chorionic gonadotropin (HCG) in females of childbearing age
Acetaminophen crosses the placenta - fetal liver is able to elaborate NAPQI by 14 weeks of gestation.
Delay in treating pregnant patients - associated with fetal demise.
A type and crossmatch should be drawn for the treatment of active bleeding in the face of coagulopathy.
Urinalysis
Proteinuria and hematuria may be seen with acute tubular necrosis (ATN), usually in conjunction with hepatic failure.
