From the FDA Drug Label
2.2 Hypertensive Patients with Left Ventricular Hypertrophy The usual starting dose is 50 mg of losartan once daily. Hydrochlorothiazide 12. 5 mg daily should be added and/or the dose of losartan should be increased to 100 mg once daily followed by an increase in hydrochlorothiazide to 25 mg once daily based on blood pressure response [see CLINICAL STUDIES (14.2)].
The adequate starting dose of Hyzaar for a 76-year-old male switching from losartan 50mg twice daily (bid) is 50mg/12.5mg (losartan/hydrochlorothiazide) once daily, as the patient is already on a dose of losartan that is equivalent to the starting dose of losartan in Hyzaar. However, since the patient is switching from a bid regimen to a once daily regimen, careful monitoring of blood pressure is recommended to determine if the dose needs to be adjusted 1.
From the Research
For a 76-year-old male switching from losartan 50mg twice daily, the appropriate starting dose of Hyzaar would be Hyzaar 50/12.5 once daily (containing losartan 50mg and hydrochlorothiazide 12.5mg). This recommendation provides equivalent losartan coverage while introducing a low dose of the diuretic component. The patient is currently taking a total of 100mg losartan daily (50mg twice daily), and while Hyzaar reduces this to 50mg daily, the addition of hydrochlorothiazide enhances the antihypertensive effect through complementary mechanisms, as shown in a study published in the Archives of internal medicine 2.
Some key points to consider when making this switch include:
- Monitoring the patient's blood pressure and electrolytes (particularly potassium) within 1-2 weeks after starting Hyzaar, as older adults may be more sensitive to diuretic effects.
- If blood pressure control is inadequate after 2-4 weeks, consider titrating to Hyzaar 100/12.5 or 100/25, depending on response, based on the patient's individual needs and response to the medication.
- The once-daily dosing of Hyzaar may improve medication adherence compared to the twice-daily losartan regimen, which is particularly beneficial in elderly patients who may be on multiple medications, as noted in a study on the clinical pharmacokinetics of losartan 3.
- The efficacy and safety of losartan 100 mg/hydrochlorothiazide 12.5 mg have been demonstrated in Japanese subjects with essential hypertension, with significant reductions in sitting diastolic blood pressure and sitting systolic blood pressure 4.
- Additionally, losartan has been shown to be effective in patients with advanced renal failure, with no significant differences in the effect on renal function, serum potassium levels, or systemic blood pressure between patients with a serum creatinine level higher than 3.0 mg/dl and those with a lower level 5.
- The optimal dose of losartan for renoprotection in diabetic nephropathy has been found to be 100 mg daily, which may be relevant for patients with diabetic nephropathy 6.