Jejunal ulceration and stricture due to wax-matrix potassium chloride tablets and amitriptyline

A 68-year-old woman presented with abdominal distention of several weeks duration and an acute small bowel obstruction. For several years she had been prescribed amitriptyline 150 mg/d, L-thyroxine 100 micrograms/d, and digoxin 0.25 mg/d. For the previous year she had been taking hydrochlorothiazide 50 mg/d and wax-matrix KCl 20 mEq/d for hypertension. At surgery a "napkin-ring" stricture of the midjejunum was found. It had microscopic features consistent with KCl local toxicity. It is speculated that delayed gastrointestinal motility secondary to amitriptyline predisposed this patient to wax-matrix KCl toxicity and that this potential side effect be considered when prescribing wax-matrix KCl.