Abuse of guaifenesin-containing medications generates an excess of a carboxylate salt of beta-(2-methoxyphenoxy)-lactic acid, a guaifenesin metabolite, and results in urolithiasis.
OBJECTIVE
Several urinary calculi were submitted to our institution for compositional analysis. The typical techniques of analysis, polarized light microscopy, electron microprobe analysis, and infrared spectroscopy proved inadequate for a definitive identification. As a result, a more detailed organic analysis was conducted to determine the exact chemical structure of the material.


METHODS
Infrared spectroscopy and mass spectrometric analysis were carried out on the solid material, providing information concerning the functional groups and the molecular mass of the organic constituent and its components. The stone was solubilized in deuterated solvents and analyzed by nuclear magnetic resonance spectroscopy, which resulted in a definitive chemical structure.


RESULTS
The spectroscopic analysis indicated that the stones were composed of a calcium salt of beta-(2-methoxyphenoxy)-lactic acid, a metabolite of the pharmaceutical guaifenesin, which is used as an expectorant.


CONCLUSIONS
Guaifenesin, an expectorant common in over-the-counter cold and allergy remedies, can cause urolithiasis if taken in excess. Discussions with physicians and their patients confirmed that most patients admitted to taking large doses of guaifenesin-containing medications.
Pickens
C L
CL
UroSciences Group, UroCor, Inc., Oklahoma City, Oklahoma 73104, USA.
Milliron
A R
AR
Fussner
A L
AL
Dversdall
B C
BC
Langenstroer
P
P
Ferguson
S
S
Fu
X
X
Schmitz
F J
FJ
Poole
E C
EC
D000293:Adolescent; D000328:Adult; D002264:Carboxylic Acids / Q000378:metabolism; D005260:Female; D006140:Guaifenesin / Q000008:administration & dosage / Q000009:adverse effects* / Q000031:analogs & derivatives* / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D012492:Salts / Q000378:metabolism; D014545:Urinary Calculi / Q000139:chemically induced* / Q000737:chemistry*
D002264:Carboxylic Acids; D012492:Salts; C002270:beta-(2-methoxyphenoxy)lactic acid; D006140:Guaifenesin