Cost sensitive prescribing

by James M Wright (2007-06-19)

The article by McAlister et al.[1] provides important information about first-line prescribing of antihypertensives and the associated laboratory testing and costs.  The authors studied patients living in Ontario 66 years of age and over, without co-morbidities, who were started on an antihypertensive drug between 1994 and 2002.  In this cohort the first-line antihypertensive classes prescribed were thiazides (39%), ACE inhibitors (30%), calcium channel blockers (15%), beta-blockers (15%), and angiotensin receptor blockers (1%).  This is comparable to a similar aged cohort in British Columbia in 1996: thiazides (41%), ACE inhibitors (24%), calcium channel blockers (15%), beta-blockers (11%) and others (9%) [2]. 

 

This is encouraging information to me as it means that despite intensive marketing of the “newer agents” (brand name ACE inhibitors, calcium channel blockers and angiotensin receptor blockers), primary care physicians are prescribing thiazides first-line about 40% of the time.  The authors have identified that the classes are similar in ability to reduce morbidity and mortality, tolerability and adherence.  Therefore the key factor in choosing between the drug classes is cost.  It is thus encouraging that the glass is 40% full, but discouraging that 60% of the time physicians do not appear to consider cost when starting antihypertensive therapy. 

 

The main conclusion of the McAlister paper [1] may help to dissuade physicians who were mistakenly persuaded to choose “newer agents”, because they led to less need for laboratory monitoring.  The authors demonstrate conclusively that the additional real-world costs associated with laboratory monitoring of thiazides are trivial in comparison to the drug acquisition costs:  approximate average 6-month laboratory plus drug acquisition costs, thiazides  ($30), ACE inhibitors ($200), calcium channel blockers ($280), angiotensin-receptor blockers ($230).  Furthermore, the small additional inconvenience of laboratory monitoring with thiazides, (0.2 extra tests per patient every 6 months) is also not a reason for not prescribing thiazides first-line.  

 

The authors have failed to list a major limitation of their study, the fact that they cannot capture or identify patients who are initially started on free samples.  This has no impact on the thiazide data as thiazide samples were not available during this time period.  It would, however, have a substantial impact on the “newer agents” prescribing data as most of these products would have had samples available.  Patients started on a sample and stopped it because it didn’t work or caused side effects are not captured in this database.  In addition patients who took a sample and had a laboratory test during the sample period would be identified as having a baseline laboratory test.  This is a problem in all administrative data studies.  As far as I am aware, there are no published studies on the proportion of new hypertensive patients, who are started on a sample.  This information is badly needed in order to interpret cohort studies such as this and since it is one of the most effective ways new drugs are marketed it is probably quite prevalent. 

 

In my opinion this is an important study that I think should encourage physicians prescribe first-line thiazides more frequently for two reasons:  1) they now know that it is common practice; thiazides are the most commonly prescribed first-line class of drugs; 2) they also now know that even when laboratory monitoring costs are included, thiazides are a bargain for the patient, and the health care system.  I believe it is time for physicians to take their role as gatekeepers of the health care system more seriously, and to become cost sensitive whenever they prescribe, independent of who is picking up tab.

 

References

 

1. McAllister FA et al.  Laboratory testing in newly treated elderly hypertensive patients without co-morbidities: a population-based cohort study.  Open Medicine vol. 1 No. 2 (2007). 

 

2. Maclure M, Dormuth C, Naumann T, McCormack J, Rangno R, Whiteside C and Wright JM. Influences of educational interventions and adverse news about calcium channel blockers on first-line prescribing of antihypertensive drugs to elderly people in British Columbia.  Lancet. 352:943-948,1998.

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