urine alkalinization

Q: Acetazolamide is a good choice for urinary alkalinization when sodium bicarbonate is contraindicated.

A) True

B) False

Answer: B

Although acetazolamide alkalinizes the urine, it simultaneously lowers the systemic pH, which defeats the purpose and may harm the patient.

Urinary alkalinization is a primary mode of treatment in many drug overdoses. All drugs that meet the following criteria can be treated with urinary alkalinization:

• predominantly eliminated unchanged by the kidney
• distributed primarily in the extracellular fluid compartment (low volume of distribution)
• minimally protein-bound
• weak acids with pKa ranging from 3.0 to 7.5

The most common are: Salicylates, Methotrexate, Barbiturates, Phenobarbital, Primidone and Sulfonamides

Using sodium bicarbonate to achieve a urine pH of 7.5 or higher while maintaining a serum pH no higher than 7.55 to 7.6 is the primary way to alkalinize urine. Unfortunately, kidney failure, pulmonary edema (volume overload), and/or cerebral edema, and severe concomitant hypokalemia are some of the contraindications for its use.

Sodium acetate as a replacement for sodium bicarbonate has been used in some cases where it is not available, though it can be given only as an infusion without a bolus (reference # 3).

#toxicology

#acid-base

References:

1. Proudfoot AT, Krenzelok EP, Vale JA. Position Paper on urine alkalinization. J Toxicol Clin Toxicol 2004; 42:1.

2. Garrettson LK, Geller RJ. Acid and alkaline diuresis. When are they of value in the treatment of poisoning? Drug Saf 1990; 5:220.

3. Neavyn MJ, Boyer EW, Bird SB, Babu KM. Sodium acetate as a replacement for sodium bicarbonate in medical toxicology: a review. J Med Toxicol 2013; 9:250.