GENE FARMA I
Generalidades
QUESTIONS/PREGUNTAS
1. A 3-year-old is brought to the emergency department having
just ingested a large overdose of tolbutamide, an oral
antidiabetic drug. Tolbutamide is a weak acid with a pKa
of 5.3. It is capable of entering most tissues, including the
brain. On physical examination, the heart rate is 100/min,
blood pressure 90/50 mm Hg, and respiratory rate 20/min.
Which of the following statements about this case of tolbutamide
overdose is most correct?
(A) Urinary excretion would be accelerated by administration
of NH4Cl, an acidifying agent
(B) Urinary excretion would be accelerated by giving
NaHCO3, an alkalinizing agent
(C) Less of the drug would be ionized at blood pH than at
stomach pH
(D) Absorption of the drug would be slower from the stomach
than from the small intestine
(E) Hemodialysis is the only effective therapy
EXPLANATION=
1. Question Analysis:
○Choice C (incorrect): Suggests weak acid is less ionized at pH 7.4
than at pH 2.0, which is wrong.
○Choice D (incorrect): Claims the ionized form is absorbed faster,
which is false.
○Choices A & B (opposites): NH4Cl acidifies urine, sodium
bicarbonate alkalinizes it.
○Correct answer (B): Use sodium bicarbonate to alkalinize the urine,
increasing ionization and trapping the weak acid.
2. Clinical Considerations:
○Urine pH manipulation can help trap drugs in their ionized form,
enhancing excretion.
