Serum potassium monitoring for users of ethinyl estradiol/drospirenone taking medications predisposing to hyperkalemia: physician compliance and survey of knowledge and attitudes.

OBJECTIVE

Yasmin-28 [ethinyl estradiol 0.03 mg/drospirenone 3 mg (EE/DRSP)] contains drospirenone, a progestin component that possesses antimineralocorticoid activity with a potassium-sparing diuretic effect similar to that in spironolactone. Product labeling recommends potassium monitoring in the first month of use for women concurrently receiving medication that may increase serum potassium.

METHODS

We evaluated compliance with this recommendation by measuring monitoring around the date of oral contraceptive (OC) initiation in women who received EE/DRSP while being treated with medications predisposing to hyperkalemia and in similar women who received other OCs. Because preliminary analyses indicated incomplete compliance, we surveyed physicians who prescribed EE/DRSP to women receiving drugs predisposing to hyperkalemia on their knowledge and attitudes with regard to the recommendation. We conducted this study using data from the Ingenix Research Datamart, which includes insurance claims for reimbursement for medical services and prescription medications for approximately 8,000,000 members of a large nationally dispersed health plan. We used claims for pharmacy dispensings of prescription medications to identify all women aged 10-59 years old who initiated EE/DRSP or other OCs during the first 3 years of EE/DRSP availability (July 2001 to June 2004). The frequency of potassium monitoring was measured by identifying claims for serum potassium tests. We conducted a telephone survey of 58 physicians who had prescribed EE/DRSP up to June 2003 to women who received concomitant hyperkalemic drugs.

RESULTS

Although potassium monitoring was generally more frequent among EE/DRSP initiators receiving concomitant hyperkalemic drugs than among other OC initiators receiving similar medications, only 40% of 466 EE/DRSP initiators with concurrent hyperkalemic treatment had potassium tests. More than 98% of surveyed physicians were aware of the potassium-sparing property of EE/DRSP. Compared with physicians whose patients had potassium tests, physicians of patients without such tests were more likely to disagree with the recommendation for users of angiotensin-converting enzyme inhibitors, angiotensin II receptor antagonists, heparin and nonsteroidal anti-inflammatory drugs. Patient barriers and health plan restrictions were other factors possibly contributing to noncompliance.

CONCLUSIONS

This study demonstrates incomplete physician compliance with a labeling recommendation of potassium monitoring for initiators of EE/DRSP receiving concomitant therapy predisposing to hyperkalemia. The limited compliance was likely due to a combination of selective physician acceptance of the recommendations and specific patient and health plan barriers to testing.