How It Works
Olmesartan/HCTZ works through two distinct pathways to lower blood pressure:
- Olmesartan: This blocks the action of angiotensin II. This hormone normally attaches to receptors on the blood vessels, causing them to constrict or narrow. By blocking this effect, olmesartan allows the blood vessels to relax and dilate, making it easier for blood to flow through them.
- Hydrochlorothiazide (HCTZ): This diuretic increases the amount of salt and water the body removes through urination. By reducing the total amount of fluid in the bloodstream, HCTZ helps lower the pressure of blood against the artery walls.
Together, these two mechanisms provide an additive effect that is more powerful than using either medication alone. This dual approach helps the heart pump blood more efficiently without having to work as hard. Standard guidelines suggest that it can take up to four weeks of consistent use to reach the full blood pressure-lowering effect of this medication.
| Quick Facts | |
|---|---|
| Common Brands | Benicar HCT |
| Drug Class | Angiotensin II receptor blocker (ARB) and thiazide diuretic |
| Generic Status | Generic version of Benicar HCT (olmesartan/hydrochlorothiazide) |
| Availability | Prescription only |
Dosing
Standard guidelines suggest a starting dose is 20 mg/12.5 mg taken by mouth once daily. This means each tablet contains 20 mg of olmesartan, which helps relax blood vessels, and 12.5 mg of hydrochlorothiazide to help remove excess fluid. Depending on how the body responds, a provider may gradually increase the dose to a maximum of 40 mg of olmesartan and 25 mg of hydrochlorothiazide per day.
This combination tablet is typically swallowed whole with or without food. Because this medication contains a diuretic, it is often recommended to take the dose in the morning or early afternoon to prevent the need for frequent urination during the night. Taking this medication at the same time daily helps the medication work consistently and ensures full benefits.
Note: Dosing information below is educational only. Your prescribing physician will determine your specific dose based on your individual health needs. Always follow your healthcare provider’s instructions for exact dosing.
Uses
FDA-Approved Uses
Olmesartan/hydrochlorothiazide is FDA-approved for the treatment of high blood pressure (hypertension) in adults.
Off-Label Uses
You may see olmesartan/HCTZ prescribed for uses that are not “FDA-approved.” This is a common and legal practice called “off-label” prescribing, where a doctor uses their clinical judgment to prescribe a drug for a different (but well-researched) purpose. Some common off-label uses include:
- Chronic kidney disease management: Some providers use this combination to help slow the progression of kidney damage in individuals with specific types of chronic kidney disease.
- Heart failure support: While not a primary treatment, this combination may be used as part of a regimen to manage fluid retention and blood pressure in people with certain stages of heart failure.
Side Effects
Most individuals tolerate this medication well, but because it affects fluid balance and blood vessel relaxation, side effects may occur. Some symptoms may lessen over time as the body gets used to the lower blood pressure. It is important to stay well-hydrated while taking this treatment to minimize the risk of dizziness or fatigue.
Common Side Effects
- Dizziness and lightheadedness
- Headache
- Nausea
- Upper respiratory infections or sore throat
- Fatigue or unusual tiredness
- Increased levels of uric acid
- Muscle cramps or back pain
- Increased urination
- Dehydration
Serious Side Effects
Serious side effects are rare, but it’s important to know what to look for if they do occur.
- Dangerously low blood pressure: Symptoms include feeling faint, severe dizziness, confusion, or pale skin. This reaction is more common when first starting the treatment or increasing the dose.
- Kidney injury: Call a provider right away in the case of decreased urination, swelling in the feet or ankles, or unexplained weight gain.
- Electrolyte imbalances: This medication can cause high or low levels of potassium, sodium, and magnesium. Signs include irregular heartbeat, extreme weakness, or muscle twitching.
- Sprue-like enteropathy: a rare intestinal condition associated with olmesartan. Symptoms include severe, chronic diarrhea and significant weight loss that can occur months or years after starting the drug.
- Vision problems: Sudden eye pain, redness, or trouble seeing distant objects can be signs of increased intraocular pressure.
- Severe allergic reaction: Seek emergency help for swelling of the face, lips, or throat, trouble breathing, or a widespread rash.
Call your doctor immediately if you experience any concerning or prolonged symptoms.
Pharmacist Tips
Take the Dose Early
Taking this medication in the morning helps prevent multiple trips to the bathroom during the night, as the diuretic component increases urination.
Monitor Blood Pressure at Home
Keeping a log of blood pressure readings helps your healthcare provider determine if the medication is working at the current dose.
Protect Your Skin From the Sun
The hydrochlorothiazide component can make the skin more sensitive to sunlight. It is recommended to wear sunscreen and protective clothing when outdoors.
Stand Up Slowly
To prevent dizziness or fainting, take your time when moving from a sitting or lying position to standing.
Avoid Salt Substitutes
Many salt substitutes contain potassium. Because olmesartan can affect potassium levels, using these products might cause the mineral to rise to dangerous levels.
Stay Hydrated
Drink plenty of water unless a provider has given specific instructions to limit fluids. Dehydration can worsen side effects like dizziness and kidney strain.
Keep Up With Bloodwork
Regular blood tests are necessary to monitor kidney function, electrolyte balance, and blood sugar levels while on this therapy.
Drug Interactions
Olmesartan/HCTZ can interact with several other medications, which may change how well they work or increase the risk of side effects.
- Nonsteroidal anti-inflammatory drugs (NSAIDs): Taking pain relievers like ibuprofen or naproxen can reduce the blood pressure-lowering effect of this medication and increase the risk of kidney damage.
- Lithium: This medication can cause lithium levels to rise to toxic amounts in the blood. Careful monitoring by a provider is required if these medications are used together.
- Diabetes medications: Hydrochlorothiazide can raise blood glucose (sugar) levels, which may require adjustments to insulin or oral diabetes drugs.
- Potassium supplements: Combination with an ARB medication such as olmesartan can lead to high potassium levels (hyperkalemia), which can affect heart rhythm.
- Alcohol: Drinking alcohol while taking this medication can increase the risk of severe dizziness and fainting due to a further drop in blood pressure.
- Cholesterol medications: Drugs like cholestyramine can prevent the body from absorbing this blood pressure medication. These should be taken at least four hours apart.
Always give your doctor and pharmacist a complete list of all your medications, vitamins, and supplements to check for potential interactions.
FAQs
What is “sprue-like enteropathy,” and why is it associated with the olmesartan component of this medication?
Sprue-like enteropathy is a rare but serious intestinal condition that causes severe, chronic diarrhea and significant weight loss. This issue is linked to olmesartan because the drug appears to trigger an unintended immune response in the digestive tract that mimics the symptoms of celiac disease. This reaction can develop even after taking the medication for a long time.
Should olmesartan/hydrochlorothiazide be taken in the morning or at night?
Providers typically recommend taking this medication in the morning. Since this combination contains a water pill that increases urination, taking it early in the day helps prevent waking at night to use the bathroom.
Does olmesartan/hydrochlorothiazide interact with nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen?
Yes, taking nonsteroidal anti-inflammatory drugs can make this medication less effective at lowering blood pressure. This combination also increases the workload on the kidneys, which may lead to kidney injury.
Can taking olmesartan/hydrochlorothiazide trigger an acute gout flare or elevate uric acid levels?
The hydrochlorothiazide component can increase blood uric acid levels. For some individuals, this change can trigger a gout attack, which causes joint pain and swelling.
Is olmesartan/hydrochlorothiazide safe for those with a sulfa allergy?
Hydrochlorothiazide is a sulfonamide derivative. While many people with a sulfa antibiotic allergy can safely take this medication, some may experience a cross-reaction. It is important to discuss any past allergic reactions with a provider.
How does olmesartan/hydrochlorothiazide affect blood glucose levels in patients diagnosed with diabetes mellitus?
This medication can cause high blood sugar (hyperglycemia). Individuals with diabetes may need to monitor their blood glucose more frequently, as the dose of diabetes medication might need adjustment.
What should I do if I miss a dose of olmesartan/hydrochlorothiazide?
Take the missed dose as soon as you remember. However, if it is nearly time for the next dose, skip the missed dose. Never take two doses at once to make up for a missed one.
Is it safe to drink alcohol while taking olmesartan/hydrochlorothiazide?
Drinking alcohol can worsen side effects like dizziness and lightheadedness. Limit or avoid alcohol, as it can cause blood pressure to drop too low when combined with this medication.
Can taking olmesartan/hydrochlorothiazide cause a persistent dry cough, similar to ACE inhibitors?
A dry cough is less common with olmesartan than with ACE inhibitors. However, a cough can still occur in some people. If a persistent cough develops, it should be reported to a provider.
How long does olmesartan/hydrochlorothiazide take to reach its full effect on lowering blood pressure?
While some reduction in blood pressure may happen within the first week, it usually takes about four weeks of daily use to see the maximum benefit of the treatment.
Does olmesartan/hydrochlorothiazide interact with lithium?
Yes, this combination can prevent the body from clearing lithium properly. This can lead to dangerously high levels of lithium in the system, so a provider must monitor lithium blood levels closely.
Comparable Medications
Olmesartan / Hydrochlorothiazide vs Olmesartan, Lisinopril-HCTZ, Azor, Tribenzor, or Telmesartan?
Olmesartan
From $32.49
This is the single-agent version of the medication without the diuretic. While it is effective at relaxing blood vessels, the combination version is often used when olmesartan alone does not lower blood pressure enough. Adding the water pill provides an additional treatment option.
Lisinopril/Hydrochlorothiazide Tablets
From $32.99
This is another combination of a blood pressure medication and a water pill. Lisinopril is an ACE inhibitor rather than an ARB. Lisinopril is more likely to cause a persistent dry cough, which makes olmesartan/hydrochlorothiazide a common alternative for those who cannot tolerate ACE inhibitors.
Amlodipine/Olmesartan Tablets
From $29.99
Amlodipine/olmesartan (Azor) is a combination medication that has olmesartan and amlodipine, a calcium channel blocker. Unlike olmesartan/hydrochlorothiazide, Azor does not contain a diuretic. This treatment is often used for individuals who need multiple medications but cannot take or do not respond well to water pills.
Olmesartan / Amlodipine / HCTZ Tablets
From $49.99
Olmesartan / amlodipine / HCTZ (Tribenzor) is a combination medication. It is used for more resistant cases of high blood pressure. Standard guidelines recommend that Tribenzor be reserved for those who require three different medications to achieve their blood pressure goals.
Telmisartan
From $26.99
This is a different medication in the same ARB class as olmesartan. Telmesartan stays in the body longer and may be used as a once-daily option.
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Important: Information on this page is for educational purposes only. Prescribing decisions are made by independent, licensed providers. TelyRx operates technology-enabled pharmacies and a telehealth platform that connects patients with licensed providers. Prescriptions, when provider-approved and issued, are filled and shipped by TelyRx-affiliated pharmacies. We do not employ physicians or make prescribing decisions. Learn more about our editorial standards here.