Malabsorption of Oral Antibiotics in Pregnancy after Gastric Bypass Surgery

Susanna R. Magee, MD, MPH; Grace Shih, MD; Anne Hume, PharmD


J Am Board Fam Med. 2007;20(3):310-313. 

In This Article

Abstract and Introduction

Gastric bypass surgery, by definition, changes the absorption capabilities of the stomach and small intestine. The use of oral medications in patients post gastric bypass may need to be adjusted by medical providers to account for this absorption change. The following case exemplifies this dilemma in a pregnant patient status post gastric bypass surgery with a complicated urinary tract infection.

The patient is a 29-year-old G2 P0101 who presented for prenatal care at 9 weeks gestation dated by last menstrual period and first trimester ultrasound. Her past medical history is complicated by morbid obesity, for which she underwent a Roux-en-Y gastric bypass in 2003. She tolerated the procedure well, and aside from a 2-week hospital stay after the surgery in 2003, she has been free of complications.

Her obstetrical history is notable for an emergent cesarean section in 1996 after developing eclampsia at 32 weeks gestation. The patient did well post cesarean section, and her now 10-year-old child has no complications from prematurity.

Before her pregnancy, she was taking only vitamin B12 and iron supplementation in oral form. At her first visit with the practice nurse (scheduled to confirm the diagnosis of pregnancy), it was noted that her urinalysis was positive for nitrites and leukocyte esterase. She also had 2+ protein in her bedside urinalysis. The patient was asymptomatic; however, it was presumed from this urinalysis that the patient had a urinary tract infection. The covering physician was consulted, and the patient was treated with oral amoxicillin. Two days later, the culture grew out > 100,000 colonies of Escherichia coli. Sensitivity testing showed that the organism was sensitive to amoxicillin that had been prescribed.

Two weeks later, the patient presented for her initial obstetrical examination. Once again, despite reported patient compliance, the urinalysis was nitrite, protein, and leukocyte esterase positive. The patient was treated this time with macrodantin. Two days later, the culture showed > 100,000 colonies of E. coli, and the specimen was found to be sensitive to both amoxicillin and marcodantin.

The physician called the patient to ensure, once again, that she was compliant. She had not missed any doses. The patient was employed as a registered nurse in the outpatient setting and was fully aware of the necessity of compliance with all medications, especially antibiotic regimens.

Two days later, the patient developed nausea, vomiting, fever to 102°F, and CVA tenderness on the right. She was sent to the hospital to be admitted for presumed pyelonephritis. Ultrasound of the kidney showed a small ( < 1 cm) nonobstructing right renal stone in the inferior pole. After 24 hours of ceftriaxone, the patient was afebrile and felt well. Urology was consulted on hospital day 2, and despite the failure of 2 outpatient regimens of oral antibiotic that were appropriate choices in terms of sensitivities, the specialist recommended amoxicillin/clavulanate as prophylaxis at 500 mg daily.

The patient was sent home on this regimen. Five days later, a test of cure analysis showed a normal urinalysis and a culture showed no growth.

After 10 days on this regimen, the patient developed fever and costovertebral angle tenderness again and was hospitalized for a second case of pyelonephritis with a pan-sensitive E. coli. She was treated with intravenous ceftriaxone for 48 hours. After much discussion regarding prophylaxis medications with maternal fetal medicine specialists, obstetricians and family physicians, the decision was made to use weekly intramuscular ceftriaxone as prophylaxis.

The patient remained infection free from that point on and went on to deliver by elective repeat cesarean section at 39 weeks gestation.


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