Research Article: The Effects of Mandatory Prescribing of Thiazides for Newly Treated, Uncomplicated Hypertension: Interrupted Time-Series Analysis

Date Published: July 10, 2007

Publisher: Public Library of Science

Author(s): Atle Fretheim, Kari Håvelsrud, Graeme MacLennan, Doris Tove Kristoffersen, Andrew D Oxman, Steve Jan

Abstract: BackgroundThe purpose of our study was to evaluate the effects of a new reimbursement rule for antihypertensive medication that made thiazides mandatory first-line drugs for newly treated, uncomplicated hypertension. The objective of the new regulation was to reduce drug expenditures.Methods and FindingsWe conducted an interrupted time-series analysis on prescribing data before and after the new reimbursement rule for antihypertensive medication was put into effect. All patients started on antihypertensive medication in 61 general practices in Norway were included in the analysis. The new rule was put forward by the Ministry of Health and was approved by parliament. Adherence to the rule was monitored only minimally, and there were no penalties for non-adherence. Our primary outcome was the proportion of thiazide prescriptions among all prescriptions made for persons started on antihypertensive medication. Secondary outcomes included the proportion of patients who, within 4 mo, reached recommended blood-pressure goals and the proportion of patients who, within 4 mo, were not started on a second antihypertensive drug. We also compared drug costs before and after the intervention. During the baseline period, 10% of patients started on antihypertensive medication were given a thiazide prescription. This proportion rose steadily during the transition period, after which it remained stable at 25%. For other outcomes, no statistically significant differences were demonstrated. Achievement of treatment goals was slightly higher (56.6% versus 58.4%) after the new rule was introduced, and the prescribing of a second drug was slightly lower (24.0% versus 21.8%). Drug costs were reduced by an estimated Norwegian kroner 4.8 million (€0.58 million, US$0.72 million) in the first year, which is equivalent to Norwegian kroner 1.06 per inhabitant (€0.13, US$0.16).ConclusionsPrescribing of thiazides in Norway for uncomplicated hypertension more than doubled after a reimbursement rule requiring the use of thiazides as the first-choice therapy was put into effect. However, the resulting savings on drug expenditures were modest. There were no significant changes in the achievement of treatment goals or in the prescribing of a second antihypertensive drug.

Partial Text: Antihypertensive medication is one of the major drug expenditures for the national drug-reimbursement scheme in Norway, adding up to around Norwegian kroner (NOK) 1,500 million per year (€180 million, US$220 million) [1], i.e., NOK330 per inhabitant (€40, US$49). This represents 10% of all registered drug sales. The use of antihypertensive drugs has been increasing steadily over many years. However, their proportional contribution to the overall drug expenditure in Norway has decreased slightly (Table 1). An estimated 6%–10% of the Norwegian population is being treated for hypertension [2].

We conducted an ITS analysis, with 11 measurements at monthly intervals before and after the intervention. We incorporated a transition period from December 2003 to February 2004. The study protocol (Text S1) is available on our Web site (

We invited 106 practices to participate, of which 64 agreed and provided us with written consent. Three practices were excluded owing to technical difficulties, and thus our analyses are based on data from 61 practices. Among these, 19 practices were from the intervention group in a trial that we had recently conducted [5], 21 practices were from the control group in the same trial, and 21 practices had not participated in the trial. The number of patients started on antihypertensive medication was similar in the two time periods (1,628 patients before and 1,580 patients after the rule was introduced). The aggregated results for before and after the intervention, as well as during the transition period, are shown in Table 2.

After the regulation was introduced making thiazides the only drugs qualifying for reimbursement for newly diagnosed uncomplicated hypertension, the rate of thiazide prescribing for this patient group increased from 10% to 25% in the practices included in our study. There was no apparent negative effect from the regulation in terms of achievement of treatment goals, the need for adding or switching to another drug class, or on the use of ACE inhibitors for heart failure or beta-blockers for coronary heart disease.



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