Usage patterns and cost analysis of antihypertensive drugs reimbursed by the national health insurance in Gabon

Abstract

Background: The ‘Caisse Nationale d’Assurance Maladie et de Garantie Sociale’ (CNAMGS), the national health insurance fund was implemented since 2007, so that every Gabonese citizen has access to quality healthcare. Currently, in Gabon, little has been done regarding a drug utilisation review and its impact on drug cost and prescribing patterns. Objective: The study aimed to review the usage patterns, and analyse the cost of antihypertensive drugs reimbursed by the CNAMGS fund. Methods: A retrospective drug utilisation review was conducted over a 12-month period (1 June 2013 – 31 May 2014) on prescription claims data, obtained from a community pharmacy in Gabon. The study population consisted of all prescriptions (N = 51 838) containing one or more antihypertensive drugs received at the pharmacy during the period of study. Information on the prescriptions and on the costs of drugs were then reported on a data capturing form and analysed using SPSS for Windows (SPSS IBM Corp., 2013). The defined daily dose (DDD), DDDs/1000 inhabitants/day and cost/DDD were used as drug utilisation metrics. Antihypertensive drugs were classified as plain formulation for those with a single active ingredient and as fixed-dose combinations for those with two or more active substances in a single drug. Drug cost was given in Central African CFA francs (ISO 4217 code: XAF). Results: 2 504 (1.2%) prescriptions for 1 586 patients containing 3 360 antihypertensive drugs were analysed. The majority of hypertensive patients were females (n = 1 097; 69.2%). The mean patient age was 56.53 ± 14.77 years (95% CI 55.80 - 57.26), and the majority of patients (51.4%) were between the ages 45 to 65 years old. Most antihypertensives were prescribed by general practitioners (n = 1108, 44.2%) and specialists (n = 1 049, 41.9%) (p < 0.0001, Cramér’s V = 0.42). Plain formulations were mostly prescribed (61.7%) as compared to fixed-dose combinations (38.3%). Calcium channel blockers were the most frequently prescribed plain formulations (22.2%), followed by diuretics and potassium sparing agents (15.4%), angiotensin converting enzyme inhibitors (8.6%), beta-blockers (6.7%), central acting agents (4.0%) and angiotensin receptor blockers (3.0%). Generic equivalents represented only 6.8% (n = 228) of all antihypertensives claimed. Antihypertensives were prescribed at 8.35 DDDs/1000 inhabitants/day for plain formulations and 4.90 DDDs/1000 inhabitants/day for fixed-dose combinations. The total cost of antihypertensive drugs amounted to 46 576 511 XAF, of which 27 217 870 XAF (58.4%) was reimbursed by CNAMGS and the remaining 19 358 641 XAF (41.6%) was the patients’ co-payments. The total cost of generic equivalents amounted to 2 117 003 XAF (4.6% of the total cost). The mean cost for a prescription for an antihypertensive drug reimbursed by CNAMGS was 10 870 ± 7 617 XAF (95% CI, 10 571 – 11 168); in which angiotensin receptor blockers appeared to be the most expensive (cost/DDD = 476.9). Diuretics and beta-blockers as plain formulations had the lowest cost/DDD ratios, at 199.8 and 191.7, respectively. These drugs were, therefore, less expensive than other antihypertensives in the study, such as angiotensin converting enzyme inhibitors (cost/DDD = 302.9), angiotensin receptor blockers (cost/DDD = 476.9), calcium channel blockers (cost/DDD = 301.8), central acting agents (cost/DDD = 315.9) and even fixed-dose combinations (cost/DDD = 439.3). It was deducted that generic substitution of captopril and amlodipine could have led to a potential saving of 0.9% and 4.5% of the total cost of angiotensin converting enzyme inhibitors and calcium channel blockers, respectively. The overall substitution where generic equivalents were available could have led to a potential saving of 4.8%, the total cost of all antihypertensives claimed during the period of study (2 246 594 XAF), or 1 313 009 XAF would have been saved by CNAMGS. Conclusion and recommendations: Diuretics as first-line therapy are less expensive for the treatment of hypertension. The CNAMGS fund has the potential to decrease medicine cost through promotion of generic prescribing and dispensing