Hypertension Canada’s 2017 Guidelines have been released outlining some key changes that are worth reviewing. I was going to write up a summary only to find one excellent summary written by Dr. Swapnil Hiremath in AJKD blog. I encourage you to check out his post here.
I do want to bring your attention to one key recommendation from the new guidelines. That is, the new guidelines bring to light that long acting diuretics such as chlorthalidone or indapamide should be preferred over hydrochlorothiazide. The main reason is that the original landmark trial ALLHAT the establishes the superior benefit of thiazide-like diuretic in preventing cardiovascular disease events utilized chlorthalidone. This point was further encouraged in the latest SPRINT trial that was published in 2015.
However in real practice, the most commonly prescribed diuretic for hypertension continues to be hydrochlorothiazide.
So why?
Chlorthalidone is not readily available. In Ontario, the only strength that is covered by the Ontario Drug Benefits Program is the 50mg tablet. Yet the usual starting dose for hypertension is 12.5mg – 25mg po daily. It is rare that we will require a dose as high as 50mg unless it is used to treat edema. So there is the initial barrier to prescribing a lower dose chlorthalidone for anyone wishing to initiate first line treatment. Of course, the pharmacy can cut the tablet in half and even in a quarter. But this may reduce the accuracy of the dose and the lifetime of the drug. If it is left for the patient to split the tablet, it is a source of potential error that we may want to avoid, especially in the elderly population or individual who may forget to split the tablet prior to administration.
What about indapamide? We do have another option to use indapamide. But have you checked out the drug shortage website? The various brands of indapamide continue to be in shortage for the last several months, making it very unreliable to source the medication. Given the ongoing shortage, we do recommend switching to hydrochlorothiazide to avoid facing any supply issue for the patients.
So while the new guidelines encourage the use of long acting thiazide diuretics such as chlorthalidone or indapamide, it seems that on an operation or logistic level, our health care system is not set up to support them. When clinicians and patients face any challenges or barriers to prescribing or taking these medications, it creates a negative perception or experience associated with these medications.
These barriers are beyond what a pharmacist or clinician can control on a day-to-day basis. Best practice guidelines should better align with the appropriate resources to ensure they can be easily executed and implemented. One important area is to ensure the drug is available in different strengths and the manufacturers are aware of changes of guidelines to ensure production is increased accordingly. Otherwise, it is nice to see the recommendation but it is not very meaningful when we cannot procure the drug, prescribe the drug or have it reimbursed by the provincial drug plans.
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