Evaluation of vitamin B12 monitoring in a veteran population on long-term, high-dose metformin therapy.

BACKGROUND: Metformin can result in vitamin B(12) deficiency, potentially leading to complications such as neuropathy. Annual monitoring of vitamin B(12) has been suggested; however, it is unknown whether current practice reflects this recommendation. OBJECTIVE: To identify vitamin B(12) monitoring patterns in patients on long-term, high-dose metformin. Secondary objective was to determine the frequency of new vitamin B(12) deficiency, anemia, and neuropathy documented after initiation of high-dose metformin. METHODS: Electronic medical records of veterans treated at the Veterans Affairs Maryland Healthcare System with high-dose metformin (≥2000 mg/day) as of November 1, 2010, were reviewed. Data regarding metformin treatment, vitamin B(12) measurements, and documentation of vitamin B(12) deficiency, cyanocobalamin supplementation, anemia, and neuropathy were collected. Subjects treated with metformin for less than 1 year or those with documented peripheral neuropathy, megaloblastic anemia, vitamin B(12) deficiency, or a condition associated with vitamin B(12) malabsorption prior to metformin initiation were excluded. RESULTS: Subjects (N = 235) had a mean metformin dose of 2050 mg/day and mean duration of treatment of 5.2 years. Sixty percent did not have vitamin B(12) measured. Of subjects receiving metformin for 10 years or more, nearly half (46%) never had vitamin B(12) measured. New documentation of vitamin B(12) deficiency or cyanocobalamin supplementation was found in 5.5% of the population, and anemia was found in 12%. Of the 14% with new neuropathy, 42% did not have vitamin B(12) measured. CONCLUSIONS: Vitamin B(12) was not routinely monitored in patients on high-dose metformin, even in those at highest risk (≥10 years of therapy), or in those with potential manifestations of vitamin B(12) deficiency (neuropathy). Cases of vitamin B(12) deficiency and resulting anemia or neuropathy may be undiagnosed and untreated because of lack of monitoring. Prospective studies examining the effect of increased vitamin B(12) monitoring on identification and treatment of vitamin B(12) deficiency in patients on metformin are warranted.

Pruritus after discontinuation of cetirizine.

BACKGROUND: Intense pruritus or itching emerging after discontinuation of cetirizine has been the subject of postmarketing reports submitted to the U.S. Food and Drug Administration (FDA), published in the medical literature, and discussed on the internet. To better understand and further investigate this adverse event, we analyzed cases of pruritus occurring after discontinuation of cetirizine in the FDA Adverse Event Reporting System (FAERS) database and medical literature. METHODS: We conducted a retrospective study to identify and describe cases of pruritus occurring after discontinuation of cetirizine in the FAERS database and medical literature through April 24, 2017. Data collected from the reports included demographic information, reason for use, serious outcome, report source, duration of cetirizine use, time to onset of pruritus after cetirizine discontinuation, presence of associated urticaria, treatment for pruritus, concomitant comorbidities and medications associated with pruritus, rechallenge information, and patient outcome information. RESULTS: We identified 146 cases of pruritus after discontinuation of cetirizine. Reporting frequency increased starting in 2008. The median patient age was 38 years (n = 141), ranging from 6 to 71 years, and cases were predominantly reported in females (n = 110). Most cases (n = 115) were submitted directly to the FDA from consumers or healthcare providers. The median duration of use of cetirizine prior to discontinuation was 24 months (n = 130), ranging from 0.3 to 172.2 months. The median time to onset of pruritus from discontinuation was 2 days (n = 91), ranging from 0.5 to 5 days. Of the 55 cases that reported discontinuation of cetirizine again after restarting, 54 reported pruritus recurrence. CONCLUSIONS: Our case series provided evidence of an association between the discontinuation of cetirizine and the development of pruritus. The mechanism by which cetirizine causes pruritus upon discontinuation is unknown. Patients and prescribers should have knowledge of this adverse event, given the widespread use and availability of cetirizine, and potential impact on patient quality of life.

Cefazolin-induced hypoprothrombinemia.

PURPOSE: A case of cefazolin-induced hypoprothrombinemia in a patient with renal failure is reported. SUMMARY: A 50-year-old African-American woman was transferred from the orthopedics service to the internal medicine service for management of acute renal failure. Before her transfer, she had spinal surgery and subsequently developed a wound infection complicated by Escherichia coli bacteremia. After trials of multiple antibiotics, she developed acute interstitial nephritis and renal failure. On the day of her transfer to the internal medicine service, i.v. cefazolin sodium 1 g was administered every 24 hours to eradicate the E. coli detected in blood cultures. Her baseline International Normalized Ratio (INR) was 1.3. On day 7 of cefazolin therapy, her INR increased to 4.0. Because of her recent history of bleeding and hypotension, vitamin K 10 mg i.v. was administered, followed by 5 mg orally for the next two days. Her INR decreased and normalized at 1.1. The patient had no changes to other drug therapies and had no medical conditions known to independently affect prothrombin time during this episode. The score on the Naranjo et al. adverse-event probability scale revealed a probable relationship between cefazolin and hypoprothrombinemia in this patient. CONCLUSION: A patient with a postsurgery wound infection and acute renal failure developed hypoprothrombinemia after receiving cefazolin for seven days.