From the FDA Drug Label
The effect of losartan is substantially present within one week but in some studies the maximal effect occurred in 3 to 6 weeks. Mean peak concentrations of losartan and its active metabolite are reached in 1 hour and in 3 to 4 hours, respectively
The onset of action for Losartan (losartan potassium) is substantially present within one week, with peak concentrations of losartan and its active metabolite reached in 1 hour and 3 to 4 hours, respectively 1.
From the Research
Losartan typically begins to lower blood pressure within 1-2 hours after taking a dose, with peak effects occurring around 6 hours post-administration. This is based on the study by 2, which found that losartan is rapidly absorbed, reaching maximum concentrations 1-2 hours post-administration. The study also found that the pharmacologically active E 3174 metabolite has an estimated terminal half-life of 6 to 9 hours, which contributes to the peak effects of losartan.
Key Points
- Losartan is rapidly absorbed, with maximum concentrations reached within 1-2 hours post-administration 2
- The peak effects of losartan occur around 6 hours post-administration, due to the contribution of the E 3174 metabolite 2
- The full therapeutic effect of losartan may not be seen until after 3-6 weeks of consistent daily use, as the body needs to adjust to the changes in the renin-angiotensin-aldosterone system
Mechanism of Action
Losartan works by blocking angiotensin II receptors, preventing the hormone from constricting blood vessels and causing the release of aldosterone, which leads to sodium and water retention. This mechanism explains why the full effect takes time - the body needs to adjust to these changes in the renin-angiotensin-aldosterone system.
Dosage and Administration
For most patients, losartan is dosed at 50 mg once daily initially, which may be increased to 100 mg daily if needed for blood pressure control. Patients should take losartan consistently at the same time each day to maintain steady blood levels and optimal effectiveness, and should continue their medication even if they feel well, as hypertension is typically asymptomatic. According to the study by 3, losartan can be administered once daily, with a sustained release formulation providing 24-hour coverage.