OLMESARTAN MEDOXOMIL AND HYDROCHLOROTHIAZIDE
Clinical safety rating: avoid
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
Olmesartan medoxomil is an angiotensin II receptor blocker (ARB) that selectively inhibits angiotensin II binding to AT1 receptors, reducing vasoconstriction and aldosterone secretion. Hydrochlorothiazide is a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule, increasing diuresis and lowering blood pressure.
| Metabolism | Olmesartan medoxomil is a prodrug that is rapidly hydrolyzed to active olmesartan by esterases in the gastrointestinal tract and liver. Olmesartan is not metabolized by CYP450 enzymes. Hydrochlorothiazide is not extensively metabolized; most is excreted unchanged in urine. |
| Excretion | Olmesartan: ~60% renal, ~35% fecal. Hydrochlorothiazide: ~70% renal (unchanged), ~30% biliary/fecal. |
| Half-life | Olmesartan: terminal half-life ~10–15 hours; no accumulation. Hydrochlorothiazide: terminal half-life ~6–15 hours; prolonged in renal impairment. |
| Protein binding | Olmesartan: >99% bound (mainly albumin). Hydrochlorothiazide: ~68% bound (albumin). |
| Volume of Distribution | Olmesartan: ~17 L (~0.24 L/kg for 70 kg). Hydrochlorothiazide: ~3–4 L/kg (extensive tissue distribution). |
| Bioavailability | Olmesartan: ~26% (oral); prodrug medoxomil cleaved to active form. Hydrochlorothiazide: ~65–70% (oral). |
| Onset of Action | Oral: olmesartan onset 1–2 h; hydrochlorothiazide onset 2 h; combined effect within 2–4 h. |
| Duration of Action | Olmesartan: 24 h (dosing once daily). Hydrochlorothiazide: 6–12 h, but combined effect up to 24 h with repeated dosing. |
| Molecular Weight | Olmesartan: 558.6 Da; Hydrochlorothiazide: 297.7 Da |
Oral, one tablet once daily. Starting dose: Olmesartan medoxomil 20 mg / hydrochlorothiazide 12.5 mg. Titrate up to maximum 40 mg / 25 mg daily as needed.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR <30 mL/min/1.73 m². For GFR 30-60 mL/min/1.73 m², use with caution; avoid thiazide diuretics if severe renal impairment. No dose adjustment needed for GFR ≥60 mL/min/1.73 m². |
| Liver impairment | Child-Pugh Class A and B: No dose adjustment. Child-Pugh Class C: Not recommended due to limited data; use with caution. |
| Pediatric use | Not approved for pediatric patients <18 years of age. Safety and efficacy not established. |
| Geriatric use | Start at lowest dose (20/12.5 mg once daily). Monitor renal function and electrolytes more frequently. Titrate slowly based on blood pressure response and tolerability. |
| 1st trimester | Avoid. Associated with fetal renal damage, oligohydramnios, and skull ossification defects. Teratogenic risk. |
| 2nd trimester | Contraindicated. Can cause fetal hypotension, renal failure, and oligohydramnios. |
| 3rd trimester | Contraindicated. Risk of neonatal hypotension, anuria, and acute renal failure. |
Clinical note
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
| FDA category | Contraindicated |
| Placental transfer | Both components cross the placenta. Angiotensin II receptor antagonists (olmesartan) and thiazide diuretics (hydrochlorothiazide) are known to cross. |
| Breastfeeding |
■ FDA Black Box Warning
WARNING: FETAL TOXICITY - Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue as soon as possible once pregnancy is detected.
| Common Effects | Dizziness Weakness Headache Tiredness Edema swelling Chest pain |
| Serious Effects |
Pregnancy (second and third trimesters)AnuriaHypersensitivity to olmesartan or hydrochlorothiazideHistory of angioedema with ACE inhibitors or ARBsSevere renal impairment (CrCl < 30 mL/min)Hepatic impairment and/or cholestasisConcomitant use with aliskiren in patients with diabetes
| Precautions | Hypotension in volume- or salt-depleted patients, Renal function impairment: Monitor serum creatinine and potassium, Electrolyte imbalances: Hyponatremia, hypokalemia, hypomagnesemia, Fetal/neonatal morbidity and mortality, Exacerbation of systemic lupus erythematosus, Acute angle-closure glaucoma (rare with hydrochlorothiazide), Non-melanoma skin cancer risk (photosensitivity with hydrochlorothiazide) |
Loading safety data…
| Hydrochlorothiazide may suppress lactation. Olmesartan excreted in minimal amounts; monitor infant for hypotension and renal effects. Use only if benefits outweigh risks. |
| Lactation Rating | L3 (Moderately Safe) - Limited data; caution advised. |
| Teratogenic Risk | First trimester: Potential risk based on drugs acting on renin-angiotensin system. Second and third trimesters: Fetal renal dysfunction, oligohydramnios, skull ossification defects, hypotension, and death. Hydrochlorothiazide may cause fetal or neonatal jaundice, thrombocytopenia. |
| Fetal Monitoring | Serial fetal ultrasound for amniotic fluid volume and renal function; monitor maternal blood pressure, renal function, and electrolytes. Consider fetal echocardiography. |
| Fertility Effects | No specific human data; animal studies show no adverse effects on fertility. Olmesartan and hydrochlorothiazide are not known to impair fertility. |
| Food/Dietary | Avoid high-potassium foods (e.g., bananas, oranges, spinach) unless instructed otherwise; limit alcohol; avoid salt substitutes containing potassium chloride; take with or without food but consistently. |
| Clinical Pearls | Monitor serum creatinine and electrolytes; risk of acute angle-closure glaucoma if sulfonamide allergy; avoid in pregnancy; use with caution in renal impairment (CrCl <30 mL/min); may cause hypotension in volume-depleted patients. |
| Patient Advice | Take exactly as prescribed, usually once daily. · Avoid alcohol and NSAIDs to prevent hypotension and kidney issues. · Do not use potassium supplements or salt substitutes without talking to your doctor. · May cause dizziness, especially when standing up; stand up slowly. · This medication can cause a serious reaction if you have a sulfa allergy. · If you miss a dose, take it as soon as you remember unless it's near the next dose; do not double. · Report symptoms like decreased urination, swelling, or vision changes immediately. · Women should not become pregnant while taking this drug; use effective contraception. |