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Simple forgetfulness plays a significant role in patients having low adherence to clopidogrel (Plavix) after percutaneous coronary intervention (PCI), researchers found.

Patients who reported difficulty remembering to take all of their medications or bringing their medications when they leave the house and missing taking their medicine in recent weeks were more likely to have low adherence to clopidogrel within 30 days of PCI, according to Paul Muntner, PhD, of the University of Alabama at Birmingham, and colleagues.

Other issues, including access to a pharmacy or doctor, cost, and comfort level between the patient and the doctor, were also significantly associated with low clopidogrel adherence, which has been linked in previous studies to higher rates of stent thrombosis in those with drug-eluting stents, the researchers reported online in the American Journal of Cardiology.

"Identifying patients who are likely to discontinue clopidogrel early or have low adherence can affect clinical decision making before PCI," they wrote. "Specifically, cardiologists may choose to use bare-metal stents or balloon angioplasty for patients they identify as likely to discontinue or have low adherence to clopidogrel after PCI."

Muntner and colleagues examined data from the Ambulatory Closure Device Percutaneous Coronary Intervention (ABCD-PCI) trial, which included patients undergoing elective PCI and aimed to assess the safety of same-day discharge.

The current analysis included 284 patients -- mean age 55.8 -- who completed a questionnaire on general medication adherence after PCI but before hospital discharge. At 30 days after PCI, the patients completed a similar questionnaire focused on clopidogrel adherence.

Adherence to daily medications was measured using the Morisky Medication Adherence Scale. Score of less than 6, of 6 to 7, and of 8 indicate low, medium, and high adherence, respectively.

Roughly one-third of the patients fell into each adherence category at baseline.

At 30 days, low adherence to clopidogrel -- defined both by a score of less than 6 on the adherence scale and discontinuation of clopidogrel -- occurred in 11% of patients.

The following factors at baseline were identified as significant predictors of low clopidogrel adherence at 30 days:

• Usually having difficulty remembering to take all medications: OR 8.81 (95% CI 3.23 to 24.0)
• Missing taking medicine in the previous two weeks: OR 4.67 (95% CI 2.13 to 10.2)
• Sometimes or often taking smaller doses of medications because of cost: OR 3.78 (95% CI 1.09 to 13.1)
• Having difficulty remembering to take all medications once in a while: OR 3.59 (95% CI 1.49 to 8.63)
• Sometimes or often having difficulty filling prescriptions: OR 3.06 (95% CI 1.36 to 6.87)
• Sometimes forgetting to take medicine: OR 3.03 (95% CI 1.43 to 6.43)
• Sometimes forgetting to bring medication when leaving home: OR 2.41 (95% CI 1.06 to 5.47).

Patients with low and medium adherence scores at baseline were also more likely to have low adherence to clopidogrel at 30 days (ORs 10.9 and 6.13, respectively, P<0.05 for both).

Not being comfortable asking a doctor for instructions (OR 3.36, P=0.05) and having difficulty reaching a primary physician (OR 2.46, P=0.06) were marginally significant predictors of low clopidogrel adherence.

"The present study suggests that it may be possible to use a few items to identify who is likely to discontinue clopidogrel after PCI," Muntner and colleagues wrote, noting that future studies are needed to develop a screening tool using a standard psychometric approach.

They acknowledged that the study was limited by the inclusion of low-risk patients enrolled in a randomized controlled trial only, the use of only 30 days of follow-up, the use of only one adherence scale, and the need to combine those who discontinued the drug with those with low adherence due to small numbers.

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