Dosage & Administration
Adult: The usual recommended initial and maintenance dose is Irbesartan 150 mg once daily, with or without food. Irbesartan at a dose of 150 mg once daily generally provides a better 24 hour blood pressure control than 75 mg. However, initiation of therapy with Irbesartan 75 mg could be considered, particularly in haemodialysed patients and in the elderly over 75 years. In patients insufficiently controlled with Irbesartan 150 mg once daily, the dose of Irbesartan can be increased to Irbesartan 300 mg, or other anti-hypertensive agents can be added. In particular, the addition of a diuretic such as hydrochlorothiazide has been shown to have an additive effect with Irbesartan. In hypertensive type 2 diabetic patients, therapy should be initiated at Irbesartan 150 mg once daily and titrated up to Irbesartan 300 mg once daily as the preferred maintenance dose for treatment of renal disease. The demonstration of renal benefit of Irbesartan in hypertensive type 2 diabetic patients is based on studies where Irbesartan was used in addition to other antihypertensive agents, as needed, to reach target blood pressure.
Elderly: although consideration should be given to initiating therapy with Irbesartan 75 mg in patients over 75 years of age, dosage adjustment is not usually necessary for the elderly
Paediatric: Irbesartan is not recommended for use in children and adolescents due to insufficient data on safety and efficacy.
Diuretics and other antihypertensive agents: prior treatment with high dose diuretics may result in volume depletion and a risk of hypotension when initiating therapy with Irbesartan.
Potassium supplements and potassium-sparing diuretics: based on experience with the use of other drugs that affect the renin-angiotensin system, concomitant use of potassiumsparing diuretics, potassium supplements, salt substitutes containing potassium or other drugs that may increase serum potassium levels (e.g. heparin) may lead to increases in serum potassium and is, therefore, not recommended.
Lithium: reversible increases in serum lithium concentrations and toxicity have been reported during concomitant administration of lithium with angiotensin converting enzyme inhibitors. Similar effects have been very rarely reported with irbesartan so far. Therefore, this combination is not recommended. If the combination proves necessary, careful monitoring of serum lithium levels is recommended.
Non-steroidal anti-inflammatory drugs: When angiotensin II antagonists are administered simultaneously with non-steroidal anti- inflammatory drugs (i.e. selective COX-2 inhibitors, acetylsalicylic acid > 3 g/day and non-selective NSAIDs), attenuation of the antihypertensive effect may occur. Additional information on irbesartan interactions: In clinical studies, the pharmacokinetic of irbesartan is not affected by hydrochlorothiazide. Irbesartan is mainly metabolised by CYP2C9 and to a lesser extent by glucuronidation. No significant pharmacokinetic or pharmacodynamic interactions were observed when irbesartan was coadministered with warfarin, a drug metabolised by CYP2C9. The effects of CYP2C9 inducers such as rifampicin on the pharmacokinetic of irbesartan have not been evaluated. The pharmacokinetic of digoxin was not altered by coadministration of irbesartan.
Pregnancy & Lactation
Pregnancy: Irbesartan is contraindicated in the second and third trimesters of pregnancy. In the second and third trimesters, substances that act directly on the renin-angiotensin-system can cause foetal or neonatal renal failure, foetal skull hypoplasia and even foetal death. As precautionary measure, irbesartan should preferably not be used during first trimester of pregnancy. A switch to a suitable alternative treatment should be carried out in advance of a planned pregnancy. If pregnancy is diagnosed, irbesartan should be discontinued as soon as possible, skull and renal function should be checked with echography if, inadvertently, the treatment was taken for a long period.
Lactation: Irbesartan is contraindicated during lactation. It is not known whether irbesartan is excreted in human milk. Irbesartan is excreted in the milk of lactating rats. Precautions: Intravascular volume depletion: symptomatic hypotension, especially after the first dose, may occur in patients who are volume and/or sodium depleted by vigorous diuretic therapy, dietary salt restriction, diarrhoea or vomiting. Such conditions should be corrected before the administration of Irbesartan.