TOXICOLOGYMultiple-Dose Activated Charcoal
Uses repeated doses of activated charcoal (every 2–4 hours) to increase poison
clearance. MDAC exerts its effects through disruption of enterohepatic circu-
lation or direct adsorption across the GI mucosal surface.
INDICATIONS
■ Drugs that have enterohepatic circulation and can possibly be treated with
MDAC include:
■ Phenobarbital
■ Carbamazepine (Tegretol)
■ Theophylline
■ Aspirin
■ Dapsone
CONTRAINDICATIONS
■ MDAC is contraindicated in the same settings as AC.
RISKS
■ The risks associated with MDAC are similar to those with AC; however,
there is a greater risk of bowel obstruction with MDAC.
Urinary Alkalinization
Urinary alkalinization attempts to increase renal elimination of a drug by
increasing urine pH. Urinary acidification to increase the clearance of weak
bases is not recommended due to the risk of renal injury.
DOSE
■ Alkalinization is accomplished via a sodium bicarbonate (NaHCO 3 ) infu-
sion.The most common method uses 150 mEq of NaHCO 3 (3 amps) in
1 L D 5 W, infused at 1.5 to 2 ×the normal IV fluid maintenance rate.
INDICATIONS
■ Urinary alkalinization only affects the clearance of drugs that are weak
organic acids.
■ Aspirin (most common use for alkalinization)
■ Phenobarbital
■ Formic acid
CONTRAINDICATIONS
■ Poisoning with agents that are not weak organic acids and are not primarily
cleared by the kidneys
■ Patients who cannot tolerate excess sodium/water loading (eg, CHF, renal
failure)
RISKS
Can precipitate hypokalemia and decrease ionized calcium levels
Hemodialysis
Hemodialysis (HD) directly removes toxins from a patient’s plasma, using the
same technology applied to renal failure.
Single-dose activated charcoal
is used to decrease poison
absorption.
Multiple-dose activated
charcoal is used to increase
poison elimination.Urinary alkalinization will
not occur unless hypokalemia
is corrected.Urinary alkalinization is used
for weak organic acids:
Aspirin, phenobarbital, formic
acid (methanol metabolite).