The prevalence of inappropriate polypharmacy related to antihypertensive medications is relatively low but estimated to have still affected 49,000 Australian adults in 2018.

Using a PBS 10% sample dataset, researchers from the University of NSW identified 425,541 adults exposed to at least one anti-hypertensive medication in 2018.

In their study,  almost half of the patients (47.5%) were receiving more than one antihypertensive medication but the proportion of patients receiving an inappropriate combination was a low 2.4%.

Inappropriate prescribing included combinations that contradicted guidelines such as concomitant use of ACE inhibitors with ARBs, and to a lesser extent the use of verapamil with beta-blockers.

In-class polypharmacy e.g. two cardioselective beta-blockers was also considered inappropriate given evidence that drugs with the same mechanism of action would have no additive antihypertensive effect.

The authors, from the Centre for Big Data Research in Health at the University of UNSW, said that proportion of inappropriate polypharmacy had dropped from 5.1% in 2013.

Not surprisingly, the study found the rates of potentially inappropriate combinations were higher among patients dispensed a higher number of medicines – from 0.7% in patients on dual therapy to 3.7% in patients with three antihypertensives and 16% of patients with four or more antihypertensive medicines.

And patients on fixed-dose combinations were less likely to have inappropriate combinations than patients on free-drug combinations. 

The authors said the findings suggested awareness of Australian hypertension management guidelines was high but with some room to improve. 

“Prescribing of fixed-dose combinations among patients on dual therapy, and further practical guidance on strategies for polytherapy, particularly among patients using a higher number of antihypertensive agents, may help further improve this guideline-concordant care.”

“While fixed-dose combinations can limit choices in the type and dosage of drugs available, they may also offer an advantage in improving adherence to therapy through a reduced pill burden,” the study said.

It noted increased vigilance was warranted for patients on more than three antihypertensives, particularly in the context of more aggressive blood pressure control targets.

And more evidence was required on the use of three and four antihypertensive drug fixed-dose combinations.

The study was published in the Journal of Hypertension.