A retrospective analysis of the prescribing patterns of hipolipidaemic drugs : a pharmacoeconomic approach
Background: More than 5.5 million South Africans aged 30 years and older are at risk of chronic disease by virtue of their triglyceride levels (Maritz, 2006:101). Dyslipidaemia is common in westernized and industrialized communities (Steyn et al., 2000:720), especially so for South Africa, where burden of disease data show dyslipidaemia to be the second most prevalent of all the chronic conditions in the country (Council for Medical Schemes, 2006:48). It is therefore no surprise that at 3.3 per cent hipolipidaemics ranked second highest based on prevalence percentage per therapeutic group in the 2005 Mediscor medicines review on South African medical claims data (Bester et al., 2005:8-11). Hipolipidaemic drugs subsequently also ranked second highest for expenditure per therapeutic group, achieving a total expenditure of 5.8 per cent. Objective: The purpose of this study was to characterise the usage and cost of hipolipidaemic drugs in the private health care environment in South Africa based on various categories, including age, sex, prescriber type and generic indicator. Methods: A quantitative retrospective drug utilisation review was performed using dispensing records from a medicine claims database. Data for a two-year period (1 Jan. 2005 to 31 Dec. 2006) were used. Hipolipidaemic medicine usage was analysed according to five patient age strata: patients younger than 9 years, 10 ≤ 19 years, 20 ≤ 45 years, 46 ≤ 59 years and older than 59 years. Basic descriptive statistics such as frequencies and arithmetic mean (average) were used to characterise the study sample, and were calculated using the Statistical Analysis System (SAS®) for Windows 9.1® program (SAS Institute Inc., 2002-2003). Results: The database consisted of 19 860 593 and 21 473 062 medicine item claims for 2005 and 2006 respectively, at a total cost of R 1 893 376 921.00 (for 2005) and R2 046 944 383.00 (for 2006). Patients receiving hipolipidaemic medicine items represented about 7.2% of the total number of patients on the database in both 2005 and 2006. About 47% of the study population in both 2005 and 2006 was female, compared to 53% males. Hipolipidaemics represented between 3.1% (N = 19 860 593) and 3.3% (N = 21 473 062) of the total number of items claimed during the study period. The total cost of hipolipidaemics accounted for between 5.6% (N = R1 893 376 921.00) and 5.8% (N = R2 046 944 383.00) of the total cost of all medications claimed during the study period. The average cost per item of hipolipidaemics was R170.63 ± 70.19 in 2005 compared to R167.08 ± 71.93) in 2006. HMG-CoA reductase inhibitors formed the leading therapeutic class in hipolipidaemic medicine items in all age groups on the database, except for children aged 0 ≤ 9 years, where the “others” group, in particular cholestyramine (Questran Lite 4 mg) was claimed more frequently. Of the items claimed for both study periods, simvastatin was the most commonly claimed, accounting for 45.35% (n = 284 232) and 46.21% (n = 325 970) respectively of the number of hipolipidaemic items claimed, at a total cost of 30.97% (n = R33 119 294.18) and 31.38% (n = R36 983 938.41) for 2005 and 2006 respectively. Non-substitutable and generic hipolipidaemic medicine items carried the largest percentage of prevalence and cost in both study periods for both sex categories and all age groups. The majority of claims for hipolipidaemic medicine items were prescribed by general medical practitioners, followed by “other prescribers” and then by cardiologists. Only a small number of prescriptions claimed were prescribed by thoracic surgeons and even fewer by pharmacotherapists and pharmacists. Trade name products that were mostly prescribed were Lipitor and Adco-Simvastatin. Of all the hipolipidaemic drugs utilised on the database, only three active ingredients (bezafibrate, simvastatin and pravastatin) had generic equivalents available at the time of the study. With total substitution (100%) of these three drugs with the average price of the available generic hipolipidaemic equivalents on the database, a cost saving of R1 744 462.27 or 1.63% (N = R106 943 348.53) was possible in 2005. In 2006, a total cost saving of R1 526 985.79 or 1.30% (N = R117 862 631.87) was calculated. Conclusion: The study highlighted the most commonly prescribed hipolipidaemics within a sub-population of South African patients. The high average cost per prescription of hipolipidaemic drugs indicates that they are relatively expensive in comparison to other medications. Generic (and therapeutic) substitution should be investigated as potential cost-saving mechanisms in the private health care sector of South Africa.
- ETD@PUK