What is the onset of action, half-life, and duration of effect of losartan (Angiotensin II Receptor Antagonist) with hydrochlorothiazide (HCTZ) (Thiazide Diuretic) after discontinuation?

From the FDA Drug Label

The terminal half-life of losartan is about 2 hours and of the metabolite is about 6 to 9 hours. The plasma elimination half-life has been reported to be 6 to 15 hours for hydrochlorothiazide. Onset of action occurs within 2 hours of dosing, peak effect is observed at about 4 hours, and activity persists for up to 24 hours for hydrochlorothiazide. The effect of losartan is substantially present within one week but in some studies the maximal effect occurred in 3 to 6 weeks. There is no apparent rebound effect after abrupt withdrawal of losartan.

• Onset of action:
  • Losartan: substantially present within one week, maximal effect in 3 to 6 weeks
  • Hydrochlorothiazide: within 2 hours of dosing
• Half-life:
  • Losartan: 2 hours
  • Losartan active metabolite: 6 to 9 hours
  • Hydrochlorothiazide: 6 to 15 hours
• Duration of effect:
  • Losartan: maintained for up to a year, no rebound effect after abrupt withdrawal
  • Hydrochlorothiazide: persists for up to 24 hours 1 2

From the Research

Losartan with hydrochlorothiazide starts working within 1-2 hours, with losartan reaching peak effects in 6 hours and hydrochlorothiazide in 2-4 hours, and its effects last for 1-2 weeks after discontinuation, as supported by studies such as 3 and 4. The combination of losartan and hydrochlorothiazide is a well-tolerated and effective treatment for high blood pressure, with losartan having a half-life of about 2 hours and its active metabolite having a longer half-life of 6-9 hours, while hydrochlorothiazide's half-life is approximately 6-15 hours, as reported in studies like 5 and 6. Some key points to consider when using this medication include:

• The full blood pressure-lowering effect typically develops over 3-6 weeks of regular use, as seen in studies such as 7 and 3.
• Common side effects may include dizziness, increased urination, and electrolyte imbalances, as noted in studies like 5 and 4.
• Regular monitoring of blood pressure and kidney function is recommended while taking this medication, as emphasized in studies such as 3 and 6.
• It's essential to take this medication consistently at the same time each day and never stop it suddenly without medical supervision, as this could cause a rebound increase in blood pressure, as warned in studies like 7 and 4.