Hydrochlorothiazide / Telmisartan

Hydrochlorothiazide/telmisartan is a combination blood pressure medication supported by two products. Here is what the FDA-approved labeling covers:

• Micardis HCT (telmisartan and hydrochlorothiazide oral tablet): approved to treat high blood pressure (hypertension) in adults, used alone or alongside other blood pressure medications
• Telmisartan and Hydrochlorothiazide tablets (generic oral tablet): approved to treat high blood pressure (hypertension) in adults, used alone or alongside other blood pressure medications
• Both products are approved only for patients who have not reached their blood pressure goal on a single drug — neither is intended as the very first blood pressure treatment
• Lowering blood pressure reduces the risk of fatal and non-fatal cardiovascular events, primarily strokes and heart attacks

This tablet pairs two blood pressure-lowering ingredients that work in different ways. Telmisartan is an ARB (angiotensin II receptor blocker) — it blocks a chemical called angiotensin II from binding to receptors in blood vessel walls. Normally, angiotensin II causes vessels to tighten and the body to hold onto sodium; blocking it lets vessels relax and blood pressure fall. Hydrochlorothiazide is a thiazide diuretic — it acts on the kidneys to flush out extra sodium and water, shrinking the volume of fluid the heart has to pump. Because the diuretic tends to lower potassium levels and the ARB tends to raise them, the two drugs partially offset each other's electrolyte effects when used together.

Both Micardis HCT and the generic telmisartan/hydrochlorothiazide tablet are taken once a day by mouth and can be taken with or without food. Dose adjustments are made by your prescriber based on how your blood pressure responds, typically re-evaluated after two to four weeks. Micardis HCT tablets should stay in their blister pack until the moment you take them.

• Patients with liver or bile duct problems should start at the lowest available combination under close medical supervision
• This drug is not recommended if you have severe kidney impairment or severe liver disease
• Never change your dose on your own — always follow your prescriber's instructions

Most people tolerate this combination well; side effects are generally mild. The most commonly reported ones include:

• Dizziness
• Upper respiratory tract infection
• Sinusitis
• Diarrhea
• Fatigue
• Nausea
• Flu-like symptoms
• Back pain, postural low blood pressure

Serious reactions are less common but important to know: sudden eye pain or vision change could be a sign of acute angle-closure glaucoma (a medical emergency); signs of low potassium (muscle cramps, weakness, irregular heartbeat) or low sodium should prompt a call to your doctor; and any swelling of the face or throat may signal a rare but serious allergic reaction and needs immediate emergency care.

• Fetal toxicity (pregnancy): This is the most urgent warning. Both ingredients can injure or kill an unborn baby, especially during the second and third trimesters. Stop the medication immediately if you become pregnant and call your doctor.
• Low blood pressure: If you are dehydrated or on high doses of diuretics, your blood pressure may drop sharply when you start this drug. Volume or salt depletion should be corrected first.
• Kidney function: This drug can worsen kidney function, particularly in people with renal artery narrowing, chronic kidney disease, severe heart failure, or dehydration. Your doctor will monitor kidney labs.
• Electrolyte imbalances: Telmisartan can raise potassium; hydrochlorothiazide can lower potassium, sodium, and magnesium. Blood tests will track these levels.
• Acute angle-closure glaucoma: Hydrochlorothiazide can rarely cause a sudden dangerous rise in eye pressure. Seek emergency care for sudden eye pain or blurred vision.
• Systemic lupus erythematosus: Thiazide diuretics have been reported to trigger or worsen lupus.
• Hypersensitivity: Allergic reactions to hydrochlorothiazide are more likely in people with a history of allergies, asthma, or sulfonamide/penicillin allergy.

Several drugs, foods, and substances can interact with hydrochlorothiazide/telmisartan:

• Aliskiren: Must not be combined in patients with diabetes; should be avoided in those with kidney disease — risk of serious kidney damage, low blood pressure, and high potassium
• Lithium: Thiazides reduce lithium clearance, raising lithium to potentially toxic levels — combination is generally not recommended
• ACE inhibitors, other ARBs, potassium-sparing diuretics, or potassium supplements: Can push potassium dangerously high when combined with telmisartan
• NSAIDs (ibuprofen, naproxen, etc.): May blunt the blood pressure-lowering effect and increase the risk of kidney problems
• Alcohol, barbiturates, or narcotics: Can intensify the blood pressure-lowering effect, increasing dizziness or fainting risk
• Corticosteroids or ACTH: Worsen the low-potassium effect of hydrochlorothiazide
• Cholestyramine or colestipol: Can reduce how much hydrochlorothiazide is absorbed from your gut
• Ramipril: Co-administration significantly increases blood levels of ramipril and its active form, which may intensify blood pressure effects

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Pregnant or trying to become pregnant: Do not take this medication — it can cause serious harm or death to the baby. Stop immediately if pregnancy is detected.
• Breastfeeding: Do not breastfeed while taking this drug; the ingredients may pass into milk and harm a nursing infant.
• Severe kidney impairment: This drug is not recommended — loop diuretics are preferred in that setting.
• Severe liver disease: Not recommended; patients with milder liver or bile duct problems must start under close medical supervision.
• Diabetes: Aliskiren must not be combined with this medication; also, hydrochlorothiazide can raise blood sugar, so blood glucose monitoring may need adjustment.
• Allergy to sulfonamides or penicillin: Higher risk of hypersensitivity reactions and acute angle-closure glaucoma from the hydrochlorothiazide component.
• Low blood volume or sodium: Correct dehydration or salt depletion before starting — risk of symptomatic low blood pressure on initiation.
• Children: Safety and effectiveness have not been established in pediatric patients.
• Older adults: Use with caution; start at the lower dose range. Greater sensitivity to blood pressure drops and electrolyte changes is possible.

Taking too much telmisartan is most likely to cause low blood pressure, dizziness, and a fast or slow heart rate. Too much hydrochlorothiazide can cause dehydration and electrolyte losses — especially low potassium, sodium, and chloride — which can lead to weakness, muscle cramps, or heart rhythm problems. If you suspect an overdose, seek emergency medical care immediately; telmisartan cannot be removed by dialysis.

Telmisartan blocks the effects of angiotensin II at the AT1 receptor, which relaxes blood vessels and reduces the body's tendency to hold onto sodium and water. In studies of people with high blood pressure, once-daily dosing kept blood pressure lower throughout the full 24-hour period between doses, with the blood pressure-lowering effect becoming maximal after about four weeks. Hydrochlorothiazide begins producing a diuretic (urine-increasing) effect within about two hours of a dose, peaking around four hours and lasting six to twelve hours.

Telmisartan is absorbed quickly after an oral dose — blood levels peak within about 30 to 60 minutes — and its effects last roughly 24 hours, which is why it is dosed once daily. It is processed in the liver (not by the CYP450 enzyme system) and eliminated almost entirely through the stool; it cannot be removed by dialysis. Hydrochlorothiazide is not broken down by the body and is cleared rapidly by the kidneys, with at least 61% leaving the body unchanged in urine within 24 hours. Both drugs can be taken with or without food, though food modestly reduces the amount of telmisartan absorbed.

Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) .