Losartan
An angiotensin receptor blocker used for high blood pressure, stroke prevention with left ventricular hypertrophy, and diabetic kidney disease.
Drug card
- How it works
- Blocking angiotensin II's AT1 receptor, so vessels relax
- Used for
- High blood pressure
- Lowering stroke risk with left ventricular hypertrophy
- Kidney disease in type 2 diabetes
- Heart failure
- Known for
- High potassium (hyperkalemia)
- Harm to the unborn baby (fetal toxicity)
- Its name
- -sartan means an angiotensin II receptor blocker (ARB)
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does losartan work?
Losartan blocks the AT1 receptor, but much of its effect comes from an active carboxylic acid metabolite formed by CYP2C9 and CYP3A4 during first-pass metabolism. By weight that metabolite is 10 to 40 times as potent, and it lasts longer (half-life 6 to 9 hours, against about 2 hours for losartan).
Like other angiotensin receptor blockers: They block the AT1 receptor, so angiotensin II can no longer narrow arterioles or drive aldosterone release: vessels relax, the kidneys keep less sodium, and potassium can rise. They act at the receptor rather than on ACE, so bradykinin does not build up and cough is far rarer than with ACE inhibitors, though angioedema can still occur.
Uses
What is losartan used for?
- High blood pressure
- Lowering stroke risk with left ventricular hypertrophy
- Kidney disease in type 2 diabetes
- Heart failure
Side effects
Side effects of losartan
- High potassium (hyperkalemia)Known forSerious
- Harm to the unborn baby (fetal toxicity)Known forSerious
- Dizziness
- Low blood pressure on starting, if salt or water depleted
- Dizziness on standing (orthostatic hypotension)
- Worsening kidney functionSerious
- Angioedema (rare)Serious
- Back pain
- Stuffy nose (nasal congestion)
- Tiredness
- Swollen legs, ankles or feet
- Hepatitis and other liver problems (rare)Serious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Liver impairment: less drug is cleared, so a lower starting dose is used.
- Its stroke benefit with left ventricular hypertrophy may not apply to black patients.
- It raises lithium levels and can cause lithium toxicity.
Good to know: Partly a prodrug: its active carboxylic acid metabolite does most of the receptor blocking.
Remember it
A way to remember it
Block the lock, not the key-maker.
ACE inhibitors stop the enzyme that makes angiotensin II (the key); ARBs leave that enzyme alone and block the AT1 receptor (the lock). Bradykinin is not built up, so the ACE inhibitor cough is rare, and ARBs are the usual swap when that cough stops an ACE inhibitor.
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Its name
-sartan means angiotensin II receptor blocker (ARB)
Sartans block the AT1 receptor for angiotensin II. Valsartan is also half of sacubitril/valsartan, which adds a neprilysin inhibitor.
- Every drug name stem
Its class
Angiotensin receptor blockers
Other angiotensin receptor blockers with a card:
Easily mixed up with ACE inhibitors and angiotensin receptor-neprilysin inhibitors.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood pressure
Losartan is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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