What is the antihypertensive mechanism of angiotensin II receptor antagonists?
Angiotensin II receptor antagonists can selectively inhibit angiotensin II receptors (especially AT1 type) to dilate blood vessels, lower blood pressure, reduce aldosterone secretion, drain sodium, and inhibit sympathetic nerves. AT1 receptors are mainly distributed in the human brain, heart, vascular smooth muscle cells, blood vessels, kidneys, adrenal cortex and placenta. When angiotensin II activates it, it will synthesize and release aldosterone, constrict blood vessels, reduce renal blood flow, increase renal tubular reabsorption of sodium, and stimulate sympathetic nerve activity. These are closely related to blood pressure levels.
The indications and dosage of allisartan.
Pharmacokinetics:
Allisartan is hydrolyzed by enzymes in the gastrointestinal tract and not metabolized by the liver. Therefore, it can significantly reduce the burden on the liver in patients with hypertension. It is well absorbed orally and its half-life is about 10 hours.
Dosage:
The initial and maintenance doses of allisartan are generally 240 mg once daily. Increasing the dose of allisartan did not significantly improve its efficacy. The maximum blood pressure lowering effect can be achieved after taking the medicine for 4 weeks. Since the absorption of allisartan is reduced by food, it is not recommended to take it with food.
Indications:
- Allisartan is effective in the treatment of mild to moderate primary hypertension. Its efficacy is similar to that of valsartan. Mild-moderate primary hypertension patients who take allisartan for a long time have high safety.
- Allisartan can improve carotid atherosclerosis. It improves intima media thickness better than valsartan.
- For patients with hypertension and stable angina, the antihypertensive effect of allisartan is more significant. In addition, it can also significantly reduce the number of angina attacks in patients.
The indications and dosage of candesartan.
Pharmacokinetics:
The efficacy of candesartan peaks 4 to 6 hours after taking the drug and then slowly declines.
Dosage:
Adults generally take candesartan 4 to 8 mg orally once a day after breakfast. Its dose can be increased to 12mg if it is necessary.
Indications:
There is clear experimental evidence that candesartan can be used in hypertensive patients with heart failure.
The indications and dosage of irbesartan.
Pharmacokinetics:
Oral administration of irbesartan is well absorbed. Its absolute bioavailability is about 60 to 80%. Its bioavailability is not significantly affected by food. Its plasma peak time is 1 to 1.5 hours. It generally has a half-life of 11 to 15 hours and reaches steady state within three days.
Dosage:
The initial and maintenance doses of irbesartan are generally recommended to be 150 mg once a day. For some special patients (such as patients undergoing hemodialysis or patients over 75 years old), the initial dose can be considered as 75 mg once a day. If the patient takes irbesartan 150mg daily and still fails to effectively control his blood pressure, it may consider increasing the dose to 300mg or adding a diuretic (such as hydrochlorothiazide). For hypertensive patients with type 2 diabetes, their initial dose was 150 mg once daily and increased to 300 mg once daily as a maintenance dose.
Indications:
Irbesartan is indicated for the treatment of hypertensive patients with type 2 diabetes mellitus or patients with primary hypertension.
The indications and dosage of losartan.
Pharmacokinetics:
Losartan is rapidly absorbed orally. It takes approximately 0.5 to 1 hour for peak plasma concentrations. It has a more obvious liver first-pass effect. Its bioavailability is about 33 to 37% and its plasma protein binding is about 98.7%. Losartan has difficulty crossing the blood-brain barrier. It has a half-life of about 1.5 to 2 hours. Losartan is metabolized to more active substances in the liver. Its metabolites have a half-life of about 6 to 9 hours. Its metabolites will enhance and prolong its antihypertensive effect.
Dosage:
The initial dose and maintenance dose are generally 50 mg once a day. The maximum antihypertensive effect will be achieved after 3 to 6 weeks after taking the medicine. For some patients, the dose can be increased to 100 mg once a day to produce a further antihypertensive effect. If the patient's blood vessel volume is insufficient (for example, the patient has taken a large dose of diuretics), the initial dose can be considered to take 25 mg once a day.
Indications:
There are treatment guidelines that losartan can be used in patients with hypertension and heart failure. In addition, there are clinical studies that losartan has the effect of increasing the excretion of uric acid. A reduction in blood uric acid levels in patients was associated with a 13 to 29% reduction in cardiovascular events.
The indications and dosage of olmesartan.
Pharmacokinetics:
Olmesartan does not affect hepatic cytochrome P450 enzymes because it is not metabolized by hepatic cytochrome P450. Its bioavailability is about 26%. Its peak plasma concentration is reached approximately 1 to 2 hours after taking the drug. Food does not affect the absorption of olmesartan.
Dosage:
The dose of olmesartan should be individualized. When it is used as a monotherapy for patients with normal blood volume, the initial dose is generally recommended to be 20 mg once a day. The dose of olmesartan can be increased to 40mg once a day for patients who still need to further lower blood pressure after taking the drug for two weeks.
Indications:
Studies have shown that olmesartan can improve cardiac function in patients with chronic heart failure. Olmesartan may be considered for the treatment of patients with chronic heart failure and hypertension.
The indications and dosage of telmisartan.
Pharmacokinetics:
Oral telmisartan is rapidly absorbed by the body. Its absolute bioavailability is approximately 50%. Food does not affect its absorption. Its half-life is greater than 20 hours.
Dosage:
The initial dose of telmisartan is 40 mg once daily. When the dose of telmisartan is 20 to 80 mg, its antihypertensive effect is dose-related. Its maximum dose is 80 mg once daily.
Indications:
Telmisartan is used to treat adults with primary hypertension. It reduces the risk of cardiovascular events.
The indications and dosage of valsartan.
Pharmacokinetics:
Valsartan generally produces its hypotensive effect within 2 hours of oral administration and reaches its maximum effect in 4 to 6 hours. The blood pressure lowering effect can last more than 24 hours. The maximum antihypertensive effect will be achieved after 2 to 4 weeks after taking the drug.
Dosage:
The recommended dose of valsartan is 80mg once a day. Food does not affect its absorption. It is recommended to take the medicine at a fixed time every day. For patients with unsatisfactory blood pressure control, the dose of valsartan can be increased to 160 mg per day or diuretics can be added.
Indications:
There is clear experimental evidence that valsartan can be used in the treatment of hypertensive patients with heart failure.
The drug interactions with angiotensin II receptor antagonists.
Irbesartan and losartan are metabolized by CYP2C9 enzymes, therefore drugs metabolized by this enzyme should not be taken together. Fluconazole and rifampin should not be used in combination with losartan. Digoxin concentrations are elevated by valsartan, so the two should not be used together. Lithium, non-steroidal anti-inflammatory drugs, potassium-sparing diuretics, etc. should be avoided in combination with all angiotensin II receptor antagonists.
What are the adverse reactions of angiotensin II receptor antagonists?
There is no significant difference in the adverse reactions of the above seven angiotensin II receptor antagonists. Common adverse reactions include hypotension, aggravation of renal artery stenosis, and elevated serum potassium. Angiotensin II receptor antagonists are contraindicated in pregnant women.
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