Case Studies

Case One: MC, an 80-year-old woman, was admitted to the hospital with a chief complaint of worsening shortness of breath and fever. Her admitting diagnosis was left lower lobe pneumonia. She was empirically started on ceftriaxone. She is wellknown to the nursing staff due to frequent bouts of pneumonia secondary to chronic obstructive pulmonary disease.

MC is 5'5" tall and weighs 130 lb. She has a history of renal failure, diabetes, and poorly controlled hypertension. On admission, her serum creatinine was 3 mg/dL, and her blood urea nitrogen was 55 mg/dL.

A sputum stain revealed many gram-negative rods. The culture grew Pseudomonas aeruginosa. The organism was susceptible only to imipenem. Upon seeing the culture and sensitivity reports, MC's physician discontinued the ceftriaxone and initiated therapy with imipenem 500 mg intravenously every 6 hours.

The pharmacist who received the imipenem order checked MC's laboratory results prior to processing the order. Because she noticed that MC's serum creatinine was elevated, she calculated MC's creatinine clearance. She discovered that MC's estimated creatinine clearance was <20 mL/min.

Should the imipenem dose be adjusted for MC's creatinine clearance?

Case Two: JB, a pharmacist in Colorado, received a panicked phone call from her parents on the East Coast. They are very concerned about JB's 16-year-old sister.

When presenting for a school physical, the pediatrician noticed that JB's sister was slightly jaundiced. Her sister denied any history of liver disease, abdominal pain, abdominal trauma, or alcohol use. She also denied taking any medications, using illicit drugs, or being exposed to toxic agents. Laboratory work showed an elevated bilirubin of 2.3 mg/dL. It also showed alkaline phosphatase and gamma-glutamyl-transpeptidase levels 4 times the normal and an aspartate transaminase within normal limits. Her white blood cell count was 7.5 x 103 cells/mm3 and she was afebrile. An ultrasound of her liver and biliary system was normal and showed no signs of biliary dilation. The pediatrician decided to refer JB's sister to a pediatric hepatologist for a liver biopsy.

JB's parents are very nervous about having their daughter undergo the biopsy procedure. After discussing the procedure with her parents, JB asked to speak with her sister. When JB's parents had left the room, her sister confessed to using oral birth control pills that she received at the local family planning clinic. Although she does not want her parents to know about the pills, she wants to know if she should have mentioned this to the doctor.

Should JB advise her sister to inform the doctor of her birth control use?

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Case One: Yes, imipenem doses are adjusted for renal impairment.The manufacturer recommends a dose of 500 mg every 12 hours in patients with a creatinine clearance <20 mL/min. The recommended dose for patients with a creatinine clearance of 31 mL/mm to 70 mL/min is 500 mg every 6 hours. For patients with a creatinine clearance of 21 mL/mm to 30 mL/mm, the dose is 500 mg every 8 hours.

Case Two: Yes, JB should advise her sister to confess her birth control use. Oral contraceptives, primarily because of their estrogen content, can cause cholestasis. This benign cholestasis generally reverses when the offending agent is discontinued.

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