Co-Diovan 160/25mg

Indications

This combination is used to treat high blood pressure.

Pharmacology

Valsartan is an oral medication that belongs to a class of medications called angiotensin receptor blockers (ARBs). It is a specific angiotensin II antagonist with oral activity, which acts on the AT1 subtype. Binding of angiotensin to its receptors causes the blood vessels to narrow (vasoconstriction), which leads to an increase in blood pressure (hypertension). Valsartan blocks angiotensin II receptors. By blocking the effects of angiotensin, valsartan can dilate blood vessels and lower blood pressure without affecting the pulse rate. The affinity of valsartan for the AT1 receptor is much higher than that for the AT2 receptor (about 20,000 times). It does not bind to or block other hormone receptors or ion channels that are known to be important for cardiovascular regulation. 

Hydrochlorothiazide is a thiazide diuretic. Thiazides affect the mechanism of renal tubular electrolyte reabsorption and directly increase the excretion of approximately the same amount of sodium and chlorine. Indirectly, the diuretic effect of hydrochlorothiazide reduces plasma volume, thereby increasing plasma renin activity, increasing aldosterone secretion, increasing urine potassium loss and reducing serum potassium. Renal aldosterone binding is mediated by angiotensin II, so co-administration of angiotensin converting enzyme (ACE) inhibitors tends to reverse the potassium loss associated with these diuretics.

Dosage & Administration

Hypertension: A patient whose blood pressure is not controlled with Valsartan and Hydrochlorothiazide monotherapy, should switch to Valsartan and Hydrochlorothiazide combination once daily. Highest allowed dose of Valsartan should not be greater than 320 mg in combination with hydrochlorothiazide 25 mg. 

For Elderly: No initial dosage adjustment is necessary for elderly patients.

Pediatric use: Safety and effectiveness in pediatric patients have not been established.

Interactions

Valsartan:

• Diuretics: Patients taking diuretics may occasionally experience excessive lowering of blood pressure after starting valsartan treatment. No interaction between thiazide diuretics and clinically important drugs has been found.
• Drugs that increase serum potassium: Since valsartan reduces the production of aldosterone, potassium supplements or salt-containing potassium substitutes may cause hyperkalemia.
• Lithium salt: Like other drugs that eliminate sodium, the clearance rate of lithium can be reduced. Therefore, if you want to use lithium salt, you must carefully monitor the serum lithium level.
• Other drugs that show interactions are warfarin and digoxin.

Hydrochlorothiazide:

• When administered at the same time, the following drugs may interact with thiazide diuretics: Alcohol, barbiturates, or anesthetics may potentiate antihypertensive effect or orthostatic hypotension may occur.
• Hypoglycemic medications (oral medications and insulin): The dose of hypoglycemic medications may need to be adjusted.
• Other antihypertensive drugs have an additive effect.
• Cholestyramine and colestipol resin: In the presence of anion exchange resin, the absorption of hydrochlorothiazide is impaired.

Contraindications

Patients who are allergic to any component of this product should not use the combination of valsartan and hydrochlorothiazide. Because it contains hydrochlorothiazide, patients who are anuria or allergic to other sulfa drugs should not use this product.

Side Effects

The combination of valsartan and hydrochlorothiazide is generally well tolerated with few side effects. The most common side effects include headache, dizziness, fatigue, abdominal pain, cough, diarrhea and nausea. Patients may also experience hyperkalemia, impotence, decreased renal function, allergic reactions, dyspnea, constipation, back pain, muscle cramps, skin rash, anxiety, insomnia, and dizziness. Low blood pressure can also occur.

Pregnancy & Lactation

Pregnancy: Valsartan should not be used during pregnancy because it can cause fetal injury or even death in the second and third trimesters. When pregnancy is detected, valsartan should be stopped as soon as possible. 
Nursing Mothers: I do not know if valsartan is excreted in human milk. Hydrochlorothiazide is excreted in human milk.

Precautions & Warnings

Impaired liver function: Since most valsartan is excreted in the bile, patients with mild to moderate hepatic impairment (including obstructive biliary diseases) should proceed with caution.  

Impaired renal function: Because thiazides can cause azotemia, patients with pre-existing renal impairment may need to reduce the dose or discontinue the drug.  

Heart failure and myocardial infarction: To be considered when initiating treatment in patients with heart failure and after myocardial infarction.

Therapeutic Class

Combined antihypertensive preparations

Storage Conditions

Store between 15-30° C.