Skip to main content

QUARTET: Quadruple UltrA-low-dose tReaTment for hypErTension

High blood pressure is common and a major cause of heart disease and stroke. While many people with hypertension are on some treatment, in over half blood pressure targets are not reached and their high blood pressure is hence uncontrolled. In this research we investigate whether an approach that combines 4 types of blood pressure lowering medications at quarter doses into one pill, may be a more effective way of controlling blood pressure and doing this with few side effects.

Primary hypothesis:

A combination pill comprising four types of blood pressure lowering medications each at ¼ standard doses will lower blood pressure more effectively than initiating patients with standard dose monotherapy as per current guideline-recommended therapy.

Study design:

A 12-week double blind randomised controlled trial comparing ultra-low dose quadruple combination therapy (LDQT) with standard dose irbesartan in participants with grade 1 and 2 essential hypertension with 12 months extension substudy to assess longer term effects and tolerability.

The QUARTET study is being conducted at various sites across the country: 

Sydney, NSW
Westmead hospital
Royal North Shore Hospital
Holdsworth House Medical Centre, Darlinghurst
Castle Hill Medical Centre, Castle Hill
Kildare Road Medical Centre, Blacktown

Perth, WA
Curtin University
Royal Perth Hospital
Sir Charles Gairdner Hospital

Melbourne, VIC
Monash University

Hobart, TAS
University of Tasmania

Ethics approval number: HREC Ref: HREC/15/WMEAD/422  

The Study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12616001144404. The ANZCTR is an open access registry that the public can use for further information.


You may be eligible to participate in this study if you HAVE the inclusion criteria and DON’T HAVE the exclusion criteria:

Inclusion Criteria:

  • Adults (≥18 years)
  • Previous documentation of hypertension or high blood pressure (SBP 140-179mmHg and/or DBP 90-109 mmHg) from GP, pharmacist or health care professional

And either:

  • A measure of Clinic SBP 140-179mmHg and/or DBP 90-109 mmHg documented by study staff in the last 12 weeks with a study automatic BP device


  • A recorded measure of daytime average SBP ≥ 135 mmHg and/or DBP ≥ 85 mmHg on a 24 hour ambulatory BP monitoring device in the last 12 weeks

And one of the following:

  • Treatment naïve (i.e. never treated)
  • Currently not on treatment (not taken in last 4 weeks)
  • Currently taking one BP lowering drug (i.e. ACE-I, ARB, CCB, BB, aldosterone antagonist, alpha-blocker)

Exclusion criteria:

  • Contraindication to irbesartan, amlodipine, indapamide or bisoprolol
  • Evidence of secondary cause of hypertension e.g. renal artery stenosis; Significant renal impairment (eGFR <50), raised serum potassium (above lab normal limit)
  • Women who are pregnant, breast feeding and/ or of childbearing potential and not using effective contraception throughout the study (pharmacological or barrier methods)
  • Concomitant illness, physical impairment or mental condition which in the opinion of the study team/ primary care physician could interfere with the conduct of the study including outcome assessments
  • Participation in a concurrent clinical trial of an investigational medical product. Patients in trials of approved medical products, or in observational, natural history and/or epidemiological studies not involving an intervention are eligible.
  • Participants responsible primary care or other responsible physician believes it is not appropriate for participant to switch current monotherapy or initiate study drug.
  • Inability or unwillingness to provide written informed consent
  • Unable to complete study procedures including 24 hour ABP
  • Definite indication for combination therapy

How to participate

If you are interested in taking part in the study please contact us:

Email :

Telephone: 02 8627 3578