The concomitant prescribing of ethinyl estradiol/drospirenone and potentially interacting drugs

Background: Ethinyl estradiol 0.03 mg/drospirenone 3 mg (EE/DRSP) contains a progestin drospirenone with antimineralocorticoid properties that may cause potassium retention leading to hyperkalemia. We estimated the percentage of EE/DRSP users prescribed concomitant potassium-sparing drugs [nonsteroidal antiinflammatory drugs, diuretics, angiotensin-converting enzyme inhibitors (with diuretics), angiotensin II agonists (with diuretics), and potassium chloride] between January 1, 2002, and March 31, 2005. Study Design: We analyzed a population-based data set of 62,527 EE/DRSP users (Dimension Rx™, Caremark). We compared the fill date and end date for each prescription (Rx) for an interacting drug to the start and end date for each EE/DRSP episode (linked Rxs). If a day of an interacting Rx overlapped with an EE/DRSP episode, concomitant prescribing was recorded. Results: A total of 17.6% of the women concomitantly used EE/DRSP and an interacting drug. Twenty-nine percent of concomitant use occurred within a month of EE/DRSP initiation. Nonsteroidal antiinflammatory drugs and diuretics were most frequently used concomitantly with EE/DRSP. Forty percent of the women with concomitant use were 35 yearsof age or older at EE/DRSP initiation compared with 29% without concomitant use (p<.001). Obstetricians/gynecologists and family practitioners were the most common prescribers of EE/DRSP and potassium-sparing drugs, respectively. Conclusions: Concomitant prescribing of EE/DRSP and potassium-sparing drugs occurred frequently in our study population. As EE/DRSP becomes more widely used, physicians prescribing it should monitor patients for potassium-sparing drug use.