Valsartan is an oral medication that belongs to a class of drugs called angiotensin receptor blockers (ARBs). It is orally active and specific angiotensin II antagonist acting on the AT1 subtype. Angiotensin's attachment to the receptors cause the blood vessels to narrow (vasoconstrict) which leads to an increase in blood pressure (hypertension). Valsartan blocks the angiotensin II receptor. By blocking the action of angiotensin, Valsartan dilates blood vessels and reduces blood pressure without affecting pulse rate. Valsartan has much greater affinity (about 20,000-fold) for the AT1 receptor than for the AT2 receptor. It does not bind or block other hormone receptors or ion channels known to be important in cardiovascular regulation.

Hydrochlorothiazide is a thiazide diuretic. Thiazides affect the renal tubular mechanisms of electrolyte reabsorption, directly increasing excretion of sodium and chloride in approximately equivalent amounts. Indirectly, the diuretic action of Hydrochlorothiazide reduces plasma volume, with consequent increases in plasma renin activity, increases in aldosterone secretion, increases in urinary potassium loss, and decreases in serum potassium. The renin-aldosterone link is mediated by angiotensin II, so co-administration of anangiotensin converting enzyme (ACE) inhibitor tends to reverse the potassium loss associated with these diuretics.

This combination is indicated for the treatment of hypertension.

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.

The combination of Valsartan and Hydrochlorothiazide is contraindicated in patients who are hypersensitive to any component of this product. Because of the Hydrochlorothiazide component, this product is contraindicated in patients with anuria or hypersensitivity to other sulfonamide-derived drugs.

The combination of Valsartan and Hydrochlorothiazide is generally well tolerated and side effects are rare. The most common side effects include headache, dizziness, fatigue, abdominal pain, cough, diarrhea and nausea. Patient may also experience hyperkalemia, impotency, reduced renal function, allergic reactions, dyspnea, constipation, back pain, muscle cramps, rash, anxiety, insomnia and vertigo. Hypotension may also occur.

Overdose Effects

Valsartan: Limited data are available related to overdosage in humans. The most likely manifestations of overdosage would be hypotension and tachycardia; bradycardia could occur from parasympathetic (vagal) stimulation. If excessive hypotension occurs, the patient should be placed in the supine position and if necessary, has to be given an intravenous infusion of normal saline. 

Hydrochlorothiazide: The most common signs and symptoms observed are those caused by electrolyte depletion (hypokalemia, hypochloremia, and dehydration) resulting from excessive diuresis. if digitalis has also been administered with it, hypokalemia, may accentuate cardiac arrhythmias. The degree to which Hydrochlorothiazide is removed by hemodialysis has not been established.

Impaired Hepatic Function: As the majority of Valsartan is eliminated in the bile, care should be exercised in patients with mild to moderate hepatic impairment including biliary obstructive disorder. 

Impaired Renal Function: Dosage reduction or discontinuation may be required with patients having pre-existing renal impairment because thiazides may precipitate azotemia. 

Heart Failure and Myocardial Infarction: Caution should be observed when initiating therapy in patients with heart failure and post-myocardial infarction patients.

Use in Special Populations

Use in Patients with Renal Impairment: The usual regimens of therapy with this combination may be followed as long as the patient's creatinine clearance is >30 ml/min. In patients with more severe renal impairment, loop diuretics are preferred to thiazides. In that case, hydrochlorothiazide is not recommended.

Use in patients with Hepatic Impairment: Care should be taken in patient with hepatic impairment.

Pregnancy & Lactation

Pregnancy: Valsartan should not be used in pregnancy, as in 2nd and 3rd trimester it can cause injury and even death to fetus. When pregnancy is detected, Valsartan should be stopped as soon as possible.

Nursing mothers: It is not known whether Valsartan is excreted in human milk. Hydrochlorothiazide is excreted in breast milk.