Losartan 100 mg pharmacology

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Losartan 100 mg Pharmacology: Mechanism of Action and Metabolism

Losartan 100 mg is an orally active, nonpeptide angiotensin II receptor blocker (ARB) that specifically blocks the type 1 angiotensin II (AT1) receptor. This action prevents angiotensin II from causing blood vessel constriction, leading to lower blood pressure and reduced workload on the heart. After oral administration, losartan is rapidly absorbed and undergoes metabolism in the liver to form an active metabolite, E-3174 (also known as EXP-3174), which has a longer half-life and greater plasma concentration than the parent drug. The active metabolite is primarily responsible for the long-lasting antihypertensive effects of losartan14.

Pharmacokinetics of Losartan 100 mg: Absorption, Distribution, and Elimination

Losartan is well absorbed, with a bioavailability of about 33%. After a single 100 mg dose, the maximum plasma concentration (Cmax) and area under the curve (AUC) increase in a dose-dependent manner. The terminal half-life of losartan ranges from 1.5 to 2.5 hours, while its active metabolite E-3174 has a half-life about twice as long. Plasma concentrations of E-3174 are consistently higher than those of losartan itself, with Cmax and AUC values for E-3174 being approximately two and five to eight times higher, respectively14. Both losartan and its metabolite are excreted via urine and bile.

Gastric emptying can influence the absorption and plasma concentration-time profile of losartan, sometimes resulting in multiple peaks in the concentration curve. Changes in gastric emptying parameters can alter the pharmacokinetic profile of both losartan and its metabolite.

Clinical Efficacy and Dosing of Losartan 100 mg

Losartan 100 mg is effective in lowering blood pressure in patients with mild to moderate hypertension. Clinical studies show that 100 mg daily provides significant reductions in both systolic and diastolic blood pressure, with effects similar to those of other antihypertensive agents such as enalapril, felodipine, and atenolol2589. The antihypertensive effect is smooth and sustained over 24 hours, and increasing the dose from 50 mg to 100 mg may provide additional benefit for patients who do not reach target blood pressure on the lower dose29.

Safety and Tolerability of Losartan 100 mg

Losartan 100 mg is generally well tolerated. The incidence of adverse effects is similar to placebo, with dizziness being the most commonly reported side effect. Most adverse events are mild to moderate and resolve without sequelae3569. In elderly hypertensive patients, the majority report no adverse events, and losartan is considered a safe option for long-term blood pressure control. There is no evidence of rebound hypertension after discontinuation.

Pharmacodynamic Effects: Renin-Angiotensin System and Uric Acid

Administration of losartan 100 mg leads to increased plasma renin activity and angiotensin II levels, reflecting its mechanism of blocking the AT1 receptor. Plasma aldosterone levels may decrease slightly, and losartan can also increase urinary excretion of uric acid without affecting creatinine excretion17. These effects are consistent with its role in modulating the renin-angiotensin-aldosterone system.

Bioequivalence and Combination Formulations

Generic formulations of losartan 100 mg have been shown to be bioequivalent to the original branded product, with similar pharmacokinetic profiles and safety. Fixed-dose combination tablets containing losartan 100 mg with other agents (such as amlodipine and rosuvastatin) have also demonstrated pharmacokinetic equivalence to separate administration, supporting their use for improved medication adherence in patients with comorbid conditions.

Conclusion

Losartan 100 mg is a well-absorbed, effective, and well-tolerated angiotensin II receptor blocker. Its antihypertensive effects are primarily due to its active metabolite, E-3174, which provides sustained blood pressure control. The drug is safe for use in a wide range of patients, including the elderly, and is available in bioequivalent generic and combination formulations, making it a versatile option for managing hypertension and related conditions12345678+2 MORE.

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Most relevant research papers on this topic

The clinical pharmacology of losartan in Japanese subjects and patients.

Losartan's long-lasting blocking effect on angiotensin II action is due to the plasma levels of its active metabolite, E-3174, rather than its main component, losartan.

RCT

1996·

42citations

·M. Nakashima et al.

Pharmacokinetic evaluation of losartan

Losartan should be prescribed at a dose of 100 mg/day or higher to maximize benefits in treating hypertension, congestive heart failure, and renal diseases.

Literature Review

2011·

29citations

·M. Burnier et al.

Pharmacokinetics, Bioequivalence, and Safety Evaluation of Two Formulations of Losartan Potassium Tablets USP 100 mg under Fasting Conditions

Losartan Potassium Tablets USP 100 mg by Caplin Point Laboratories Ltd. is bioequivalent to COZAAR® and well-tolerated under fasting conditions, supporting its potential as a cost-effective and accessible therapeutic alternative for managing hypertension.

RCT

2025·

0citations

·Gunasakaran Sambandan et al.

Modelling gastric emptying: A pharmacokinetic model simultaneously describing distribution of losartan and its active metabolite EXP‐3174

The developed population pharmacokinetic model accurately describes the disposition of losartan and its active metabolite EXP-3174, allowing for changes in gastric emptying parameters to alter concentration-time profiles and plasma oscillations.

2020·

11citations

·E. Karatza et al.

Efficacy and safety of losartan.

Losartan is an effective and well-tolerated antihypertensive agent, with a smooth antihypertensive profile and similar effects to other drugs, with dizziness being the most common adverse experience.

RCTLarge Human Trial

1995·

17citations

·A. Goldberg et al.

Farmacovigilancia con losartan de 100 mg en adultos mayores hipertensos atendidos en el Hospital María Lorena Serrano Aguilar.

Losartan 100 mg is a safe and effective treatment for hypertension in older adults, with only 16% experiencing side effects.

Observational Study

2017·

0citations

·Ortega Tillaguango et al.

Effects of losartan on blood pressure, plasma renin activity, and angiotensin II in volunteers.

Losartan administration (100 mg/day for eight doses over 9 days) leads to treatment-related decreases in blood pressure and increases in plasma renin activity and angiotensin II octapeptide in healthy male volunteers.

RCTHighly Cited

1993·

140citations

·M. R. Goldberg et al.

Clinical experience with the angiotensin II receptor antagonist losartan. A preliminary report.

Losartan is a promising antihypertensive drug with a 50mg dose being the minimal dose needed to produce significant day-long decreases in blood pressure, similar to enalapril, and a low incidence of adverse events.

Highly Cited

1992·

81citations

·Michael A. Weber

Comparative antihypertensive effects of losartan 50 mg and losartan 50 mg titrated to 100 mg in patients with essential hypertension.

Losartan 50 mg and 100 mg titrated to 100 mg effectively lower sitting diastolic blood pressure in patients with mild-to-moderate hypertension, with no evidence of rebound hypertension.

RCTLarge Human Trial

1997·

57citations

·Leila S. Ikeda et al.

Comparison of Pharmacokinetics of a Fixed-Dose Combination of Amlodipine/Losartan/Rosuvastatin with Concomitant Administration of Amlodipine/Losartan and Rosuvastatin in Healthy Volunteers

The fixed-dose combination of amlodipine/losartan/rosuvastatin 5/100/20 mg is a pharmacokinetically equivalent replacement for concomitant administration, potentially improving medication compliance in patients with hypertension and dyslipidemia.

RCTRigorous Journal

2020·

3citations

·D. Y. Yoon et al.

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