The KARTAN study: A postmarketing assessment of Irbesartan in patients with hypertension

Abstract

Background: An important purpose of postmarketing surveillance of drugs is to better characterize the safety profile of drug therapy in the clinical setting. Another goal is to confirm the effectiveness of these drugs in patients who are candidates for antihypertensive therapy and who may have been excluded from Phase III studies. Irbesartan is a long-acting angiotensin II-receptor blocker specific for the angiotensin 1-receptor subtype that, in clinical trials in patients with hypertension, reduces blood pressure. Objectives: The KARTAN (this word was derived from the first and last syllables of Karvea® [trademark of Bristol-Myers Squibb Group, Madrid, Spain] and irbesar tan) study was designed to confirm and extend the findings from previous clinical trials using data from a large number of patients with hypertension treated with irbesartan in routine clinical practice. The primary goal was to assess the types and incidences of adverse drug reactions (ADRs) occurring at a low frequency (<0.05%) with irbesartan. The secondary objectives were to study the effect of irbesartan as an antihypertensive agent, to assess the types and incidences of the most frequent ADRs (≥0.05%) occurring in routine clinical practice, and to detect possible interactions between irbesartan and other drugs frequently used in the primary care setting. Methods: This 6-month, observational, open-label, uncontrolled, national, longitudinal, prospective study was conducted by 852 primary care physicians across Spain. Men and women aged ≥18 years with mild to moderate hypertension who, in their physicians' opinion, should have been treated with irbesartan were included. Each patient was followed up for 6 months, attending visits at baseline (ie, the start of treatment) and 1, 3, and 6 months after the start of treatment. A sample size of 3219 patients was calculated for the detection of ≥1 low-incidence (<0.05%) ADR. After the baseline visit, therapy typically was begun with irbesartan 150 mg/d. The initial dose was titrated up, at 300-mg increments based on the patient's response, at each visit as needed to achieve the treatment goals (systolic blood pressure, <140 mm Hg; diastolic blood pressure, <90 mm Hg). Information regarding ADRs was collected on case-report forms designed for each visit and analyzed by the scientific committee of the study. All recruited patients were included in the tolerability analysis. Results: A total of 4887 patients were enrolled (2165 men, 2 772 women ; mean [SD] age, 61.1 [11.0] years [range, 19–94 years]; 23.3% of patients were aged >70 years); 4612 were assessable for efficacy. One hundred eight patients (2.2%) experienced ADRs over the 6-month treatment period; 3 of these patients (0.1%) experienced >1 ADR. Of the total number of clinical manifestations of ADRs, 24 occurred at an incidence <0.05%. Irbesartan produced reductions in blood pressure that were statistically significant from the first visit (all P < 0.001), and 39.9% of the patients achieved the treatment goal at the end of the follow-up period. Conclusion: In this postmarketing surveillance study of patients with hypertension treated in routine clinical practice, irbesartan showed a satisfactory tolerability profile that was consistent with that seen in randomized, controlled trials.