Toxicology Flashcards
Define pharmacokinetics
ADME
What body does to drug
Define pharmacodynamics
What drug does to body
Name 4 pharmacological problems with phenytoin
• Narrow therapeutic index (toxicity may mimic seizure)
• zero order kinetics (non-linear): enzyme responsible for its metabolism becomes saturated within therapeutic range. Elimination decrease at higher concentration
• different patients may need different doses to reach effect (steady state)
• presence of drugs metabolised through same enzyme may alter kinetics
Name 2 pharmacological problems with digoxin
• Cleared through kidneys so nb to monitor toxicity and adherence
• hypokalaemia potentiates digoxin! (Drug inhibits Na/K/ATPase pump)
Name 2 features of digoxin toxicity and how it can be treated
• Nausea vomiting
• Dysrhythmia’s - can be confused with underlying disease
Treat with antidigoxin antibodies
Name 2 pharmacological problems with lithium
• Optimum therapeutic range varies
• nephrotoxic (excreted here), can cause diabetes insipidus
How is lithium toxicity treated
Increase urinary excretion eg high fluid intake
Dialysis may be necessary if severe
Name 2 pharmacological problems with acetaminophen
• Hepatotoxic : metabolised here into mostly harmless metabolites excreted in urine, but some hepatotoxic NAPQI formed through mixed function oxidase. Usually detoxified by conjugation with glutathione but glutathione has limited supply. Thus high doses toxic
• and nephrotoxic at high doses
Name 7 signs and symptoms of paracetamol poisoning
<24h
.Nausea and vomiting, anorexia
24-48 hours
• abdominal pain, hepatic tenderness
• prolonged prothrombin time (inr)
• elevated plasma aminotraensferares and bilirubin
> 48 h
• jaundice, liver failure
• encephalopathy
. AKI
How should paracetamol poisoning be managed and monitored (7)
• N acetylcysteine at least 4 hours after ingestion:promotes hepatic glutathione synthesis, repair oxidative damage
• activated charcoal only beneficial if give within an hour of ingestion
• supportive : hydration, 5% dextrose
• severe may need liver transplant
• prothrombin time = best marker of severity
• increase in serum creatinine and metabolic acidosis > 24 h after overdose = poor prognosis
• must test drug levels, liver and renal function
Scientific name for paracetamol?
Acetaminophen
Scientific name for aspirin?
Acetylsalicylic acid
Name 5 signs of salicylate poisoning
• Earliest: tinnitus ( when > 350mg/l)
• stimulate respiratory centre → resp alkalosis at first
• metabolic acidosis later
• uncoupling of oxidative phosphorylation (inhibit ATP synthesis)
• stimulate central emetic effect
How is aspirin poisoning managed and monitored (5)
• NaHC03 to keep urine alkaline > 7.5 because salicylic acid can’t be ionized and excreted in acidic environment
• don’t exceed ph 8 - risk renal stones
• supportive : lots of iv fluids to induce diuresis, 5% dextrose, activated charcoal as aspirin is absorbed slowly in git
. If severe, haemodialysis
• monitor plasma salicylic acid levels for efficacy of treatment
Name 5 features of iron toxicity
• Cause necrosis of git mucosa → haemorrhage, fluid and electrolyte loss
• encephalopathy
• circulatory collapse
• renal failure
• liver necrosis
