losartan
Meaning of losartan: Blocking the receptor rather than the enzyme is what spares this drug the persistent dry cough that its older cousins provoke.
Definition of losartan
Losartan is a medication for high blood pressure belonging to the angiotensin II receptor blockers, often shortened to ARBs. Angiotensin II is a hormone that tightens blood vessels and prompts the body to hold on to salt and water. Losartan occupies its receptor so the signal cannot land, vessels relax, pressure falls, and strain on the heart and kidneys eases.
How does it work?
The kidney releases an enzyme called renin whenever it senses that blood pressure or salt delivery has dropped. That starts a chain ending in angiotensin II, which narrows arteries, triggers the hormone aldosterone so that sodium and water are retained, and over years drives thickening of the heart wall and stiffening of vessels. Losartan sits on the receptor that angiotensin II must bind to, leaving the hormone circulating but unheard. The result is lower high blood pressure, less fluid retention, and less of the long-term remodeling. Losartan itself is only partly active; the liver converts much of it into a metabolite that binds the receptor more tightly and lasts longer.
How does it differ from an ACE inhibitor?
| Losartan and other ARBs | ACE inhibitors | |
|---|---|---|
| Point of action | Blocks the receptor | Blocks the enzyme that produces angiotensin II |
| Effect on bradykinin | Unchanged | Allowed to accumulate |
| Dry cough | Uncommon | A frequent reason for stopping |
| Potassium and kidney effects | Similar | Similar |
The cough is the practical difference and it comes from bradykinin, a peptide that ACE also breaks down. Blocking the enzyme leaves bradykinin to build up in the airways; blocking the receptor does not, which is why an ARB is the usual substitute when a cough develops.
What else is it used for, and what effects are known?
Beyond blood pressure it is used in congestive heart failure and in kidney disease caused by diabetes, where reducing pressure inside the filtering units lowers protein loss and slows decline. Losartan also has a mild effect of lowering uric acid, unusual within its class. Recognized effects include dizziness on standing, a rise in blood potassium, and a rise in creatinine on a kidney function test when kidney blood flow depends on angiotensin II, as it does when the arteries to the kidneys are narrowed. Drugs acting on this system are avoided in pregnancy because they interfere with development of the fetal kidneys.
Also known as
Used in a sentence
Losartan was prescribed to help manage the patient's blood pressure.
Good to know
Losartan blocks the angiotensin II receptor directly, which distinguishes it from ACE inhibitors, a related class that instead reduces the formation of angiotensin II itself.