OBJECTIVES: Describe characteristics of drug prescribing patterns of antihypertensive agents using sequence analysis. With frequent changes in drug classes, sequence analysis can help illustrate the number and length of different drugs prescribed for treatment. METHODS: Medstat's MarketScan Database from 2003-2004 was used to identify a sample of newly diagnosed hypertensive patients with 6 months continuous follow-up administrative claims data. Drugs evaluated in each follow-up month were ACEI, ARB, BB, CCB, diuretic, combination AHY regimens, or none. For each patient, a sequence pattern is defined as an ordered list of drugs prescribed. Characteristics of patterns are described and visualizations were made using index plots and parallel-coordinates plots. RESULTS: Eighty-seven different sequences were identified among 387 patients studied. The three most frequent sequences observed were 6 continuous months on diuretic (16%), 6 months on ACE (14%), and 6 months on BB (12%). Nineteen percent of patients had no drug after the first month, 40% had at least one month on “no” drug, and the average duration on “no” drug was 1.4 (SE=.05) months. Patients used an average of 1.7 (SE=.1) different drugs. Thirty-eight percent of patients had some diuretic use and 15% had 6 months on diuretic. There were no significant age or gender differences in number and average length of drug episodes (a string of months on same drug), but females had more and longer episodes of “no” drug. Index plots with drug episodes characterized by different colors show changes among diuretics occur quicker and more frequently than among other drug classes. CONCLUSION: Sequence analysis is used in many scientific fields and is an unused tool that health economics can use for summarizing changes in antihypertensive and other medications.