Prescribing patterns of angiotensin-converting enzyme inhibitors for the period 2001 until 2006

Abstract

ACE inhibitors alone normalize blood pressure in approximately 50% of patients with mild- to- moderate hypertension, and many consider ACE inhibitors as first-line drugs for the treatment of high blood pressure (Jackson & Garrison, 1996:747). In addition to this ACE inhibitors have been demonstrated to be cost-effective in congestive heart failure and their cost is decreasing. There may be therefore a true need to encourage increasing use of ACE inhibitors in patients with chronic heart failure, particularly in general practice, to provide cost-effective optimal treatment in health care systems with limited financial resources (Szucs, 1997:278S). The objectives of this study were to investigate the prescribing patterns and cost of angiotensin-converting enzyme (ACE) inhibitors. The method included a longitudinal retrospective drug utilisation study, done on ACE inhibitors claimed through a national medicine claims database in a sector of the private healthcare system in South Africa. The periods were divided into 2001-2002, 2004, 2005 and 2006. The periods of 2004, 2005 and 2006 were then subdivided into four monthly periods, but not 2001-2002, because it was only used as an instrument for comparison purposes, as there were no changes in pricing regulations. The results showed that the contribution made by ACE inhibitor containing prescriptions to the total number of prescriptions showed a continuous decrease of 0.57% (n=77853) from 2004 until 2005 and then a decrease by 0.89% (n=49450) from 2005 until 2006. The total number of ACE inhibitor items claimed through the database showed a decrease of 0.54% (n=78447) from 2004 until 2005 and then a larger decrease of 0.57% (n=49661) from 2005 until 2006. The prevalence of ACE inhibitor innovators as part of all innovators decreased by 0.66% (n=53292) from 2004 until 2005 and decreased further by 0.25% (n=26678) from 2005 until 2006. The contribution made by the ACE inhibitor generics as percentage of all generics showed a decrease of 0.38% (n=25155) from 2004 until 2005 and a further decrease of 1.18% (n=22983) from 2005 until 2006. The decrease might be attributed to the reduction in the number of medical schemes from 2004 until 2006. On 2 August 2004 the "full" implementation of the pricing regulations was experienced and thus showed the lowest average cost per item for ACE inhibitors of R134.60 ± R73.83. The average cost per ACE inhibitor item decreased with 12.86% (R24.02) from Jan 2004-Apr 2004 (phase before the pre-implementation phase of the pricing regulations) until May 2004-August 2004 (pre implementation phase of the pricing regulations). After that the average cost per ACE inhibitor item decreased by 27.92% (R52.14) from May 2004-Aug 2004 until Sept 2004-Dec 2004. Even though the average cost per ACE inhibitor item increased and decreased during 2004 to 2006, the overall average cost decreased by 5.43%. The reduction might be due to the increased utilisation of generics as well as the influence of the single exit price. Cardiovascular, antihypertensive and ACE inhibitor items showed that the total cost as percentage of all medicine items decreased from 2004 until 2006 by 4.36%, 2.12% and 0.98% respectively. This might be due to the reduction in the number of prescriptions from the database. ACE inhibitor innovator and generic items showed a reduction in expected cost saving percentage with the SEP from Sept 2004-Dec 2004 until Sept 2005-Dec 2005 of 0.49% and 0.65% respectively. The expected cost savings of total ACE inhibitor items decreased with 0.42%. The active ingredient with the highest prevalence percentage during 2001-2002 was enalapril (15.21%) followed by perindopril (15.10%). From 2004 until 2006 the items with the largest prevalence percentage were perindopril and indapamide/perindopril. Both of these active ingredients showed a continuous increase in prevalence percentage from 2004 to 2006. It is also recommended to determine ACE inhibitor use and cost in specific diseases, as well as combination therapy with other antihypertensive medicines.