"How it works" series: Vancomycin

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Vancomycin was the first antibiotic developed of the glycopeptide class.  It is termed "glyco-" because it has two saccharides and "peptide" because it has seven peptides, making a structure larger than almost all other antibiotics.  The main mechanism of action is inhibition of cell wall synthesis.  Under normal conditions in bacteria, as the cell wall is being formed,

Metformin in kidney dysfunction - restriction revised

Metformin is the preferred initial pharmacologic therapy in every patient with type 2 diabetes mellitus who does not have a contraindication or intolerance.  It is recommended as monotherapy after diagnosis, continued when adding other medications (including insulin regimens), and should even be considered to prevent diabetes in certain patients (see who at the bottom).  

Old labeling

From approval, the restriction on metformin related to kidney function was as follows

"How it works" series: Linezolid

Linezolid (Zyvox) is one of only two antibiotics currently on the market in the oxazolidinone class (see what the other one is at the bottom of this article).  The unique structure makes cross resistance to other antibiotics like beta-lactams or vancomycin unlikely.  It works by binding to the 50S subunit of ribosomes in bacteria, preventing it from joining its partner 30S subunit.  In stopping the 50S subunit from binding the 30S subunit, the completed complex (70S) is never formed and therefore cannot begin to

Legionnaires' disease - reliability of urine antigen testing

A 58 year old male patient presents to the emergency room with shortness of breath for the last few days.  He also complains of chills, a cough, myalgia, and diarrhea.  His notable findings include WBC = 14 k/uL, Scr = 1.2 mg/dL, BUN = 27 mg/dL, BP = 132/76 mm Hg, RR = 30 breaths/minute, Tmax = 38.5⁰C, and O2sat = 92% on room air.  His chest x-ray reveals a patchy infiltrate suggestive of pneumonia.  Upon further questioning, the patient tells you he lives across the street from an apartment building where several people recently were diagnosed with Legionnaires' disease.  He has no recent exposure to any health care settings, has taken no antibiotics, was not recently incarcerated, is not immunocompromised, and has not recently traveled.  Can we use urine antigen testing to help guide our treatment of this patient's pneumonia?

Warfarin dosing nomogram for initiating therapy

A 60 year old female patient presents to the emergency department with complaints of swelling and pain in her right leg.  She recently had her knee replaced and has healed well since the procedure.  She has a PMH of HTN and CKD (Stage IV).  She has no other complaints at this time.  She is diagnosed with a proximal DVT on lower extremity ultrasound and the decision is made to anticoagulate her with warfarin plus a parenteral anticoagulant.  Her baseline INR is 1.28.  What strategy can we use to initiate her on warfarin to reach a therapeutic INR in a reasonable amount of time without overanticoagulating her?

Dabigatran reversal with idarucizumab (Praxbind)

A 77 year old black patient is admitted to the hospital for a gastrointestinal bleed.  He has a past medical history of CAD (MI 15 years ago), CKD (stage 4), atrial fibrillation, PUD, and hyperlipidemia for which he is taking ASA 81 mg daily, metoprolol tartrate 50 mg twice a day, atorvastatin 20 mg daily, lisinopril 20 mg daily, omeprazole 20 mg daily, and dabigatran 75 mg orally twice a day.  Initial labs indicate an aPTT of 95 seconds, hemoglobin of 6.8 g/dL, and serum creatinine 2.3 mg/dL.