New dual and triple antihypertensive combinations PBS listed — be aware of potential confusion

Most people will require more than one drug to control their blood pressure. Adding a second or third drug from a different pharmacological class at low doses can significantly improve blood pressure, and minimise adverse effects, compared with increasing the dose of a single drug.^4–6

Combination therapies have been shown to provide additional blood pressure-lowering:

• olmesartan with amlodipine combination therapy reduced blood pressure more than monotherapy^7–11
• triple therapy with valsartan, amlodipine and hydrochlorothiazide reduced blood pressure more than any of the dual therapy combinations.^12–14

With multiple single and combination products now available (see Table 1), there may be potential for patient confusion, particularly when a new brand or combination is prescribed. This is because the brand names of some combination products do not clearly indicate that these are combinations.

If prescribing fixed-dose combination therapy, ensure that patients and carers stop their previously prescribed single-ingredient medications and return them to their pharmacist for safe disposal. Advise them to become familiar with the active ingredients, dose, appearance and packaging of the new combination tablets.

Olmesartan is available in three formulations (Table 1):

• as a single active ingredient (Olmetec)
• in combination with hydrochlorothiazide (Olmetec Plus)
• in the new combination with amlodipine (Sevikar).

Note that the fixed-dose combination of olmesartan 20 mg / amlodipine 10 mg is not available in Australia. For patients whose hypertension is not adequately controlled with olmesartan 20 mg / amlodipine 5 mg, the dose can only be increased by moving to olmesartan 40 mg / amlodipine 5 mg.

Table 1.
Olmesartan and valsartan products

* Note that the fixed-dose combination of olmesartan 20 mg / amlodipine 10 mg is not available in Australia

Valsartan is available in four formulations (Table 1):

• as a single active ingredient (Diovan)
• in combination with hydrochlorothiazide (Co-Diovan)
• in combination with amlodipine (Exforge)
• in the new triple combination with amlodipine and hydrochlorothiazide (Exforge HCT).

If blood pressure is not controlled adequately with valsartan 160 mg monotherapy, consider adding an antihypertensive drug from a different class. Increasing the valsartan dose to 320 mg provides only marginal additional blood pressure reduction, which is unlikely to be clinically meaningful, and increases the risk of adverse reactions.¹⁵

There are a number of factors to consider before prescribing combination therapy (Table 2). Ideally, first establish the effective dose of, and patient response to, each individual drug in the combination.⁴ Discuss the consumer medicine information leaflet of the combination product with the patient.

Monitor patients for electrolyte status and renal function before and after starting any antihypertensive combination therapy, after each dose increment or if clinical circumstances change and are likely to worsen renal function (e.g. dehydration).

Table 2.
Combination therapy — factors to consider

For more information see:

• the NPS RADAR review Olmesartan medoxomil (Olmetec) monotherapy or in combination with hydrochlorothiazide (Olmetec Plus) for hypertension
• the NPS RADAR review Valsartan (Diovan) and combinations with hydrochlorothiazide (Co-Diovan) or amlodipine (Exforge)
• NPS Prescribing Practice Review 52: Treating Hypertension.