Antidotes (Exam 1 Cut Off) Flashcards
Properties of Ideal Antidote
- Completely reverses or neutralizes the effects of the poison
- No action of its own
- Easy to administer
- No unpleasant SE
Chelators
- EX: Dimercaprol (BAL), penicillamine, DMSA, EDTA, Deferoxamine (used for Fe)
- BAL: pain, peanut allergy
- EDTA: nephrotoxicity
- Deferoxamine: hypotension, anaphylactoid rxn, ARDS
Chronic Lead Poisoning
- KUB: gastric lavage
- Whole bowel irrigation
- Aggressive hydration
- BAL: 4-5 mg/kg IM 4h if Pb >= 70 mcg/dL
- PO DMSA + IV EDTA preferred
Iron Chelation
- Deferoxamine colorless compound when Fe+3 is removed
- Avidly binds to iron form ferrioxamine
- Eliminated urine is “pink rose” color - endpoint of therapy
Iron Poisoning
- KUB for retained pills
- Fe++ > 500 mcg/dL or > 350 mcg/dL with symptoms
- WBC > 15, BS > 150
- TIBC useless
- Lavage? WBI, aggressive fluids
- IV Deferoxamine 15 mg/kg/hour, NMT 24 hours
Antivenins/Biologics
- Crotalidae Antivenin: rattlesnake
- Lactrodectus Antivenin: black widow spider
- Elapidae antivenin: eastern/texan coral snake
- Trivalent botulinum: Botulism types A, B, and E
- Digoxin Immune Fab: digoxin/digitoxin poisoning
Digoxin Immune Fab Indications/Dosing
- K > 5.5 mEq/L, progressive heart block, Ventricular dysrhytmias, CV collapse
- Dose >= 10 mg in adults of 0.1 mg/kg in children
- # vials = serum levels x weight in kg/100
- Must measure > 6 hours after last dose OR # vials = dose in mg/0.5 mg/vial
N-acetylcysteine
- For APAP Poisoning
- Prevents NAPQI binding at hepatocyte
Naloxone
- For Opioid poisoning
- Opioid receptor antagonist
Flumazenil
- For Benzo poisoning
- Benzo receptor antagonist
- Can be CI due to risk of seizures, reversing dependence
Atropine
- For OP and carblnsecticides poison
- Muscarinic receptor antagonists
Fomepizole
- For Methanol and ethylene glycol poisoning
- Blocks metabolite formation
- Potential ADH competitive inhibitor
- Prolongs half life, methanol from 20 to 54 hours, and ethylene glycol from 4 to 20 hours
- Often need hemodialysis for methanol
- Dose: 15 mg/kg IV then 10 mg/kg q12h x 4 doses, then 15 mg/kg q12h
- If hemodialysis is needed, give every 4 hours
Idarucizumab
- For dagibatran poisoning
- Monoclonal antibody
Coagulation Factor XA recombinant
- For apixaban/rivaroxaban poisoning
- Binds and sequesters Xa inhibitors
Prussian Blue
- For thalium cesium isotopes poisoning
- Binds and inactivates thallium and cesium
Glucarpidase
- For methotrexate poisoning
- Enzymatic cleavage of methotrexate
Silymarin
- For amantoxin poisoning
- Unclear mechanism, but likely antioxidant
Nomogram
- Cannot plot a level prior to 4 hours: starts at elimination phase and peak level is 1-2 hours
- Cannot plot chronic supratherapeutic levels
- Slope is based on 4 hour half-life: most have a shorter one
- Toxic 4 hour level is 150 mcg/mL: mental math for other times (8 = 75, 12 = 37.5, etc.)
Anaphylactoid Rxn Risk
- More common in lower APAP levels
- 25% if APAP < 150, but only 3% if APAP > 300
- APAP decreases histamine release from mononucleocytes and mast cell (dose-dependent)
Antidotes + Preventing Hypoglycemia + Sulfonylurea Overdose
- Oral dextrose
- IV dextrose
- Sumatriptan
- Octreotide
Why glucose fluctuations?
- Duration of drug longer than duration of glucose
- Glucose enters the beta cell without insulin
- Sulfonylurea blocks closure of K-ATP channel
- Additional glucose yields additional insulin
Octreotide
-Somatostatin analog, blocks beta-cell calcium channels to reduce insulin secretion
Doses
-Children: 1-1.5 mcg/kg IV or SC followed by 2-3 more doses 6 hours apart
-Adult: 50-100 mcg SQ or IV, followed by three 50 mcg doses every 6 hours
-During treatment, IV dextrose infusion should be gradually tapered off
HIE Therapy Maintenance
- High dose insulin euglycemia
- Insulin: 1 unit/kg/hour, increasing by 0.5 unit/kg/hour every 30 minutes up to max of 15
- Titrate to BP (MAP >= 60), no effect on HR
- Use concentrated as 5,000u in 500 mL NS
- Glucose bolus of 0.25 g/kg if glucose <200
- Start D5W or D10W at 0.15 g/h
- Maintain serum K+ at 2.5-2.8 mEq/L, permissive hypokalemia might be helpful
HIE Pitfalls
- Stopping insulin before stopping pressor: pressor-sparing
- Stopping insulin and glucose at the same time: continue glucose 24-36 hours after D/C insulin
- volume overload if insulin is dilute
L-Carnitine Rational
- High first pass, only 15% oral bioavailability
- Manufacturer suggests q3-4h, never q<6h
- Mechanism: clears acyl CoA esters by forming acylcarnitine, shifts metabolism of VPA away from hepatoxic metabolites
- Reverses acquired urea cycle defect, resolving hyperammonemia
L-Carnitine Indications
- Serum VPA > 450 mcg/mL
- Severe coma
- Hyperammonemia (>80 mcg/dL)
- CCB overdose refractory to pressors and HEI: increases calcium channel sensitivity, decreases insulin resistance, facilitates metabolism of FFAi
