Irbesartan and Hydrochlorothiazide

Pronunciation

(ir be SAR tan & hye droe klor oh THYE a zide)

U.S. Brand Names

Avalide®

Synonyms

Avapro® HCT; Hydrochlorothiazide and Irbesartan

Generic Available

Canadian Brand Names

Avalide®

Use

Combination therapy for the management of hypertension

Pregnancy Risk Factor

C/D (2nd and 3rd trimesters)

Pregnancy Implications

See individual agents.

Lactation

Enters breast milk/contraindicated

Contraindications

Hypersensitivity to irbesartan, hydrochlorothiazide, thiazides, sulfonamide-derived drugs, or any component of the formulation; hypersensitivity to other A-II receptor antagonists; bilateral renal artery stenosis; anuria, renal decompensation; pregnancy (2nd and 3rd trimesters)

Warnings/Precautions

Based on irbesartan component: Avoid use or use smaller doses in patients who are volume depleted; correct depletion first. Deterioration in renal function can occur with initiation. Use with caution in unilateral renal artery stenosis and pre-existing renal insufficiency; significant aortic/mitral stenosis. Safety and efficacy have not been established in pediatric patients.

Based on hydrochlorothiazide component: Avoid in severe renal disease (ineffective). Electrolyte disturbances (hypokalemia, hypochloremic alkalosis, hyponatremia) can occur. Use with caution in severe hepatic dysfunction; hepatic encephalopathy can be caused by electrolyte disturbances. Gout can be precipitate in certain patients with a history of gout, a familial predisposition to gout, or chronic renal failure. Cautious use in diabetics; may see a change in glucose control. Hypersensitivity reactions can occur. Can cause SLE exacerbation or activation. Use with caution in patients with moderate or high cholesterol concentrations. Photosensitization may occur. Correct hypokalemia before initiating therapy. Chemical similarities are present among sulfonamides, sulfonylureas, carbonic anhydrase inhibitors, thiazides, and loop diuretics (except ethacrynic acid). Use in patients with sulfonamide allergy is specifically contraindicated in product labeling, however, a risk of cross-reaction exists in patients with allergy to any of these compounds; avoid use when previous reaction has been severe.

Adverse Reactions

See individual agents.

Drug Interactions

Irbesartan: Substrate of CYP2C8/9 (minor); Inhibits CYP2C8/9 (moderate), 2D6 (weak), 3A4 (weak)

Also see individual agents.

Mechanism of Action

Irbesartan: Irbesartan is an angiotensin receptor antagonist. Angiotensin II acts as a vasoconstrictor. In addition to causing direct vasoconstriction, angiotensin II also stimulates the release of aldosterone. Once aldosterone is released, sodium as well as water are reabsorbed. The end result is an elevation in blood pressure. Irbesartan binds to the AT1 angiotensin II receptor. This binding prevents angiotensin II from binding to the receptor thereby blocking the vasoconstriction and the aldosterone secreting effects of angiotensin II.

Hydrochlorothiazide: Inhibits sodium reabsorption in the distal tubules causing increased excretion of sodium and water as well as potassium and hydrogen ions

Dosage

Dose must be individualized. A patient who is not controlled with either agent alone may be switched to the combination product. Mean effect increases with the dose of each component. The lowest dosage available is irbesartan 150 mg/hydrochlorothiazide 12.5 mg. Dose increases should be made not more frequently than every 2-4 weeks.

Patient Education

See individual agents. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to become pregnant. Do not breast-feed.

Dental Health: Effects on Dental Treatment

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

No information available to require special precautions

Mental Health: Effects on Mental Status

May cause anxiety, dizziness, nervousness

Mental Health: Effects on Psychiatric Treatment

May decrease lithium clearance resulting in an increase in serum lithium levels and potential lithium toxicity; monitor serum lithium levels

Dosage Forms

Tablet:

Irbesartan 150 mg and hydrochlorothiazide 12.5 mg

Irbesartan 300 mg and hydrochlorothiazide 12.5 mg

International Brand Names

Avalide® (CA)

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