Volume 176 - Issue 4
PBS/RPBS cost implications of trends and guideline recommendations in the pharmacological management of hypertension
Authors: Mark R Nelson, John J McNeil, Anna Peeters, Henry Krum and Christopher M Reid
Med J Aust 2002; 176 (4): 189-190. || doi: 10.5694/j.1326-5377.2002.tb04358.x
Published online: 18 February 2002
Published online: 18 February 2002
In reply: We thank Pekarsky and Ewald for their comments.
It is difficult to estimate the percentage of patients on monotherapy from any source. We used data from IMS Health (http: //www.ims-global.com/) to determine the number of person-years of exposure to drugs prescribed with a principal indication of hypertension. Some of these drugs were prescribed as a sole agent if the script was for this single drug alone. Exposure for such agents was expressed as a percentage of the total exposure of this drug. For example, angiotensin-converting enzyme (ACE) inhibitors were sole agents in 63.9%. In the other 36.1%, the co-prescribed drugs may have been another antihypertensive drug or another type of drug altogether. Corresponding figures for calcium-channel blockers were 61.3%, for diuretics 53.6%, and for β-blockers 60.0%. As an approximation, we used the estimation that 60% of patients were likely to have been on monotherapy for hypertension. Adding the number on monotherapy for each drug gives an estimate of 1.2 million for the total population on monotherapy for hypertension. Therefore, the total number on drugs is likely to be greater than the 1.2 million as estimated in our article. However, the essential figure is that of 1.2 million for monotherapy, which we stand by.
It is true that a minority of prescriptions (16%) are written for people without a concession card and that these are more likely to pay the full cost of a cheaper drug. Our economic perspective was that of the PBS/RPBS. Hence, consumer costs were only included where the government made a copayment. It is acknowledged in the Methods section that "with some drugs, the patient copayment covers the total cost; in these instances the Commonwealth makes no contribution to the cost and these prescriptions are not recorded in the PBS/RPBS data" (page 566). It is also stated in the Discussion that the PBS/RPBS captures "much more of the cost of the newer, more expensive agents than thiazide diuretics or β-blockers" (page 567).
We chose to limit our sensitivity analysis to the key issue of redistribution of agents after initiation of monotherapy. The data we presented allow interested parties to conduct their own further sensitivity analyses, such as those suggested by Pekarsky and Ewald.