OBJECTIVES: Initiation of antihypertensive medication with combination therapy requires less treatment modifications which may result in lower healthcare costs compared with initiation of antihypertensive monotherapy. We compared direct medical costs for patients with hypertension who initiated antihypertensive medication with combination therapy versus monotherapy in a US integrated healthcare system.

METHODS: We identified adults with hypertension who initiated 1) angiotensin converting enzyme inhibitor (ACEI)/thiazide diuretic combination, 2) ACEI monotherapy, or 3) thiazide diuretic monotherapy between 2008 and 2014 and followed them up to three years. The adjusted annual mean healthcare costs (2021 US dollars) associated with initial ACEI/thiazide diuretic combination therapy compared with initial ACEI monotherapy were estimated using generalized linear models adjusting for patient and clinical characteristics using inverse probability of treatment weights. The analyses were repeated using initial thiazide diuretic monotherapy as a comparison group and office visit, laboratory costs, separately.

RESULTS: Of 117,949 patients, 47% initiated ACEI/thiazide combination therapy, 30% initiated ACEI monotherapy and 22% initiated thiazide diuretic monotherapy. The total adjusted annual mean healthcare costs for ACEI/thiazide combination therapy and ACEI monotherapy were $4,064 and $4,196 (∆=-$133; 95% CI -$273, +$7; p=0.06), respectively. The office visit and laboratory costs for ACEI/thiazide combination therapy were lower compared with ACEI monotherapy (office visit $595 and $613 [∆=-$18; 95% CI -$27, -$9; p<0.01]; laboratory $379 and $390 [∆=-$10; 95% CI -$15, -$5; p<0.01] for ACEI/thiazide combination and ACEI monotherapy, respectively). Compared with thiazide diuretic monotherapy, patients with ACEI/thiazide combination therapy had similar total adjusted annual mean costs ($3,650 and $3,693 for ACEI/thiazide combination and thiazide diuretic monotherapy, respectively, p=0.51) and had lower office visit [-$28 (95% CI -$37, -$19; p<0.01)] and laboratory costs [-$16 (95% CI -$22, -$11; p<0.01)].

CONCLUSIONS: Compared with initiating monotherapy, initiating ACEI/thiazide diuretic combination therapy was associated with modestly lower office visit and laboratory costs.