Retrospective analysis of the prescribing patterns of calcium channel blockers in a section of the private health care sector of South Africa
Background: Calcium channel blockers are mainly divided into antihypertensive and antianginal treatment agents. In 2000 it was estimated that 972 million adults worldwide were living with hypertension and it is expected to affect 1.56 billion patients by 2025. The incremental expenditure for the antihypertensive therapeutic group in the United States of America was estimated at $US 55 billion per annum in 2006. It was stated that around seven million people in the United States of America suffered from angina, with around 400 000 new reports every year. Objective: To determine the prescribing patterns of calcium channel blocker medicine items during 2005 to 2008 in a section of the private health care sector of South Africa. Methods: A retrospective quantitative drug utilisation review was done using a medicine claims database ranging over four years from 1 January 2005 to 31 December 2008. The total medicine claims database was divided into cardiovascular medicine items and then into calcium channel blockers. These were analysed according to age as well as gender. Further analysis included adherence of calcium channel blockers as well as an analysis of prescribers of these items during the study period. Results: The total number of patients on the medicine claims database consisted of 1 509 621 patients in 2005. This number decreased to 974 497 patients in 2008. The most medicine items were dispensed in 2006 (n = 21 113 422) with an average cost of R 92.82 (SD = 196.42) per medicine item. It was noted that 16.05% (n = 242 264) of patients used at least one cardiovascular item in 2005. The percentage of cardiovascular medicine item users increased by 4.36% during the study period to 20.41% (n = 198 847) in 2008. In 2008 the cardiovascular medicine items dispensed were responsible for 19.18% (R 342 565 308.41) of the total cost of all medicine items claimed. In 2005 the results revealed that 1.63% (n = 318 258) of all medicine items dispensed were calcium channel blocker medicine items. The percentage of calcium channel blockers increased to 2.24% (n = 367 437) of the total number of medicine items in 2008. The cost prevalence index was calculated for the calcium channel blockers and the value declined from 1.5 in 2005 to 1.22 in 2008, which indicated that the items dispensed were relatively expensive, but less than in 2005. An increase of 16.17% in the usage of generic medicine items were noted from 2005 to 2008. More female patients than male patients claimed medicine items during the study period. A higher percentage of male patients used a cardiovascular medicine item as well as calcium channel blockers during the study period compared to females and a larger percentage of their medicine expenditure was used on cardiovascular medicine items as well as calcium channel blockers compared to females. The usage of cardiovascular medicine items as well as calcium channel blocker medicine items increased with patient age. In 2008, 17.98% of patients older than 65 years of age used a calcium channel blocker compared to 0.97% of patients aged > 25 <= 35 years. Only 60.34% of calcium channel blockers items were used with acceptable refill adherence rates during the study. More than a third of the calcium channel blockers medicine items used had unacceptable low adherence rates from 2005 to 2008. In each of the study years the highest potential saving with generic substitution was seen with amlodipine containing items. It was also observed that some generic substitutions could be relatively more expensive than the innovator products and an increased cost instead of a saving through generic substitution may have occurred. Conclusion: This study highlighted the prescribing patterns and cost implications of calcium channel blockers in the private health care sector of South Africa. It is recommended that a more in–depth study of the adherence of calcium channel blockers be done. This study should also include the cost strategies of generic substitution of calcium channel blockers in South Africa.
- ETD@PUK