Sulfamethoxazole/trimethoprim and increase in serum creatinine: When to be concerned

A 65 year old male is being treated for an infection on his forearm that developed purulent drainage within the last few days.  He denies experiencing any penetrating trauma to his arm and denies any other complaints at this time.  He weighs 70 kg, His WBC count is 14.7 x 109/L, serum creatinine is 1.3 mg/dL, and his vital signs are within normal limits.  His past medical history includes hypertension and an MRSA infection last year.  He is currently taking valsartan 160 mg daily and chlorthalidone

"How it works" series: Midodrine

Midodrine is a peripherally-acting selective alpha1 receptor agonist.  Let's take that sentence apart to see what we should expect from this medication.  Being an alpha1 agonist, this means that it binds to the alpha1 receptor and activates it, causing it to perform the function that it would usually perform if its endogenous catecholamine (ie. norepinephrine) were to bind to it. 

Nitrofurantoin in renal impairment

A 74 year old female patient presents to clinic describing dysuria and urinary frequency that started within the last few days.  She has no vaginal discharge or irritation and has no CVA tenderness, fevers, chills, flank pain, nausea, or vomiting.  The diagnosis of uncomplicated UTI is made based on clinical suspicion and you decide to prescribe some antibiotics.  She weighs 72 kg and her SCr is 1.4 mg/dL.  Using the Cockcroft-Gault equation,

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