Participants' views of ultra-low dose combination therapy for high blood pressure: a mixed-methods study from the QUARTET trial.

Single-pill combination therapy containing four quarter-dose medications for high blood pressure improves BP control compared to monotherapy, however patient-reported acceptance of the quadpill as a treatment strategy remains undescribed. We collected within-trial feedback and interviewed participants from the quadruple ultra-low-dose treatment for hypertension (QUARTET) trial to characterise patient attitudes to this intervention. All trial participants were asked about ease and preference for the quadpill and provided an opportunity to give further comments on the trial at 12 weeks (trial primary endpoint) and 52 weeks extended follow-up. Separately, we used purposive and quota sampling for the semi-structured telephone interviews, with the resultant verbatim transcripts analysed using an inductive thematic analysis approach. Themes were re-evaluated after each successive interview, and at suspected data saturation, an additional interview conducted for confirmation. At 12 weeks follow-up, 502 of 591 (85%) participants responded to acceptability questions, and 359 of 417 (86%) responded at week 52. Most reported the trial capsule easy or very easy to take. From eight sites, 16 participants were interviewed between 5 August 2020 and 19 November 2020. All described a positive experience, preferred once-daily morning dosing and found routine facilitated adherence. Participants valued individual responsibility for adherence, and involvement of the general practitioner in blood-pressure management. Most reported capsule size did not deter adherence but desired a smaller capsule. Participants described a preference for minimising number and dosage of medications, reduced capsule size, and once-daily morning dosing. These findings suggest a preference for single-pill combination therapy for blood pressure lowering.