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Interactions between Avapro and Prazosin

1 drug interaction and 16 additional warnings found for the following 2 drugs:

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Drug interactions

Moderate drug interactions

Moderate:

prazosin irbesartan

Applies to: prazosin and Avapro (irbesartan)
Monitor

Additive hypotensive effects may occur when nitrates and/or antihypertensive agents are used in combination with alpha-1 antagonists. In the presence of additional blood pressure lowering agents, the risk and/or severity of first-dose effects associated with alpha-1 antagonists such as hypotension, postural hypotension, and syncope may be increased. The proposed mechanism is additive vasodilatory effects. In a multicenter, randomized, open-label study including 335 patients with a clinical diagnosis of benign prostatic hyperplasia and/or lower urinary tract symptoms, alfuzosin 10 mg was associated with significant reductions in systolic and diastolic blood pressure in those with uncontrolled hypertension when taken alone or in combination with antihypertensive agents.

Management

Caution and clinical monitoring are advised during concomitant use of alpha-1 antagonists with nitrates and/or antihypertensive agents. Lower initial dosages of the alpha-1 antagonists should be considered and gradually titrated to desired effect, while the antihypertensive or nitrate dosage may also need to be reduced. Hemodynamic responses should be monitored during coadministration, especially during the first few weeks of therapy. Patients should be advised to take the alpha-1 antagonist at bedtime, avoid rising abruptly from a sitting or recumbent position, and notify their doctor if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.

References (9)
  1. (2022) "Product Information. Xatral SR (alfuzosin)." Sanofi-Aventis Australia Pty Ltd
  2. (2021) "Product Information. Alfuzosin (alfuzosin)." Sanis Health Inc
  3. (2025) "Product Information. Alfuzosin Hydrochloride (alfuzosin)." Apotex Corporation
  4. (2025) "Product Information. Besavar XL (alfuzosin)." Zentiva Pharma UK Ltd, 2
  5. Zhang LT, Lee SW, park k, et al. (2015) "Multicenter, prospective, comparative cohort study evaluating the efficacy and safety of alfuzosin 10 mg with regard to blood pressure in men with lower urinary tract symptoms suggestive of benign prostatic hyperplasia with or without antihypertensive med" Clin Interv Aging, 10, p. 277-86
  6. (2024) "Product Information. Cardura (doxazosin)." Viatris UK Healthcare Ltd
  7. (2024) "Product Information. Hytrin (terazosin)." Waymade Ltd
  8. (2023) "Product Information. Prazosin Hydrochloride (prazosin)." Alembic Pharmaceuticals
  9. (2025) "Product Information. Silodosin (silodosin)." Ajanta Pharma USA

Food/lifestyle interactions

Moderate food/lifestyle interactions

Moderate:

irbesartan Food/Lifestyle

Applies to: Avapro (irbesartan)
Generally avoid

Moderate-to-high dietary intake of potassium, especially salt substitutes, may increase the risk of hyperkalemia in some patients who are using angiotensin II receptor blockers (ARBs). ARBs can promote hyperkalemia through inhibition of angiotensin II-induced aldosterone secretion. Patients with diabetes, heart failure, dehydration, or renal insufficiency have a greater risk of developing hyperkalemia.

Management

Patients should receive dietary counseling and be advised to not use potassium-containing salt substitutes or over-the-counter potassium supplements without consulting their physician. If salt substitutes are used concurrently, regular monitoring of serum potassium levels is recommended. Patients should also be advised to seek medical attention if they experience symptoms of hyperkalemia such as weakness, irregular heartbeat, confusion, tingling of the extremities, or feelings of heaviness in the legs.

References (2)
  1. (2001) "Product Information. Cozaar (losartan)." Merck & Co., Inc
  2. (2001) "Product Information. Diovan (valsartan)." Novartis Pharmaceuticals
Moderate:

prazosin Alcohol (Ethanol)

Applies to: prazosin
Generally avoid

The concurrent use of ethanol and alpha-1 adrenergic blockers may cause increased hypotensive effects. Patients with aldehyde dehydrogenase deficiencies (primarily Asians) may be at a higher risk of this interaction. The mechanism has not been determined. Data exist for prazosin and other alpha adrenergic blockers are expected to interact also. In addition, any patients taking alpha adrenergic blockers may experience excessive orthostatic hypotension with ethanol ingestion, due to ethanol's unopposed vasodilatory effects in the presence of alpha adrenergic blockade.

Management

Patients who develop a flushing reaction after ethanol ingestion (indicates a possible aldehyde dehydrogenase deficiency) should be advised to avoid ethanol or limit their intake. All patients should be warned about the possibility of orthostatic hypotension with concurrent ethanol use.

References (2)
  1. Kawano Y, Abe H, Kojima S, Takishita S, Omae T (2000) "Interaction of alcohol and an a1-blocker on ambulatory blood pressure in patients with essential hypertension." Am J Hypertens, 13, p. 307-12
  2. (2002) "Product Information. Xatral (alfuzosin)." Sanofi-Synthelabo Canada Inc

Disease interactions

14 potential interactions Applies to: 13 conditions, including Heart Failure, Diarrhea, Hypotension, Syncope, and Hyperkalemia.

Autonomic Neuropathy

Moderate:

prazosin

Prazosin has a moderate potential interaction with Autonomic Neuropathy.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

Biliary Obstruction

Moderate:

prazosin

Prazosin has a moderate potential interaction with Biliary Obstruction.

Little data exist concerning the pharmacokinetic disposition of prazosin in patients with liver disease. Prazosin is known to be metabolized by the liver and subsequently excreted in the bile, primarily as metabolites. Some of the metabolites are pharmacologically active and possess 10% to 25% of the hypotensive activity of prazosin. Therapy with prazosin should be administered cautiously in patients with significantly impaired hepatic or biliary function, since drug and/or metabolite accumulation may occur.

Dehydration

Major:

Avapro

The irbesartan in Avapro has a major potential interaction with Dehydration.

Angiotensin II receptor (AR) antagonists can cause symptomatic hypotension in patients with an activated renin-angiotensin system, such as volume- and/or sodium-depleted patients. Therapy with AR antagonists should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if high doses were used or if recently instituted; those on dietary salt restriction; renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with AR antagonists, and the patient should be hemodynamically stable. Ideally, patients at risk for excessive hypotension should initiate AR antagonist therapy under close medical supervision, preferably with a lower dose, and followed closely for the first 2 weeks of treatment and whenever the dosage of AR antagonist or diuretic is increased.

Moderate:

prazosin

Prazosin has a moderate potential interaction with Dehydration.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

Diarrhea

Moderate:

prazosin

Prazosin has a moderate potential interaction with Diarrhea.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

Heart Failure

Moderate:

Avapro

The irbesartan in Avapro has a moderate potential interaction with Heart Failure.

Angiotensin II receptor (AR) antagonists can cause renal impairment in patients whose renal function depends on the activity of the renin-angiotensin-aldosterone system. In addition, symptomatic hypotension can occur in susceptible individuals, which may compromise renal and myocardial perfusion. In patients with severe congestive heart failure (CHF), treatment with AR antagonists has been associated with oliguria and/or progressive azotemia and, rarely, renal failure, myocardial ischemia, and death. Therapy with AR antagonists should be initiated cautiously in patients with severe CHF, especially when accompanied by volume and/or sodium depletion. In patients who experience a decline in renal function, discontinuation of AR antagonist therapy is usually not required provided there is symptomatic improvement of the heart failure and renal deterioration is well-tolerated. Transient hypotension is also not a contraindication to further treatment with AR antagonists, since therapy can usually be reinstated without difficulty after blood pressure stabilizes.

Hemodialysis

Major:

Avapro

The irbesartan in Avapro has a major potential interaction with Hemodialysis.

Angiotensin II receptor (AR) antagonists can cause symptomatic hypotension in patients with an activated renin-angiotensin system, such as volume- and/or sodium-depleted patients. Therapy with AR antagonists should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if high doses were used or if recently instituted; those on dietary salt restriction; renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with AR antagonists, and the patient should be hemodynamically stable. Ideally, patients at risk for excessive hypotension should initiate AR antagonist therapy under close medical supervision, preferably with a lower dose, and followed closely for the first 2 weeks of treatment and whenever the dosage of AR antagonist or diuretic is increased.

Hyperkalemia

Moderate:

Avapro

The irbesartan in Avapro has a moderate potential interaction with Hyperkalemia.

Drugs that inhibit the renin-angiotensin, such as angiotensin II receptor antagonist system can cause hyperkalemia. Concomitant use of these agents with drugs that increase potassium levels may increase the risk of hyperkalemia. Use caution when using these agents together and monitor serum potassium periodically.

Hyponatremia

Major:

Avapro

The irbesartan in Avapro has a major potential interaction with Hyponatremia.

Angiotensin II receptor (AR) antagonists can cause symptomatic hypotension in patients with an activated renin-angiotensin system, such as volume- and/or sodium-depleted patients. Therapy with AR antagonists should be administered cautiously in such patients and in those predisposed to hypovolemic or hyponatremic states (e.g., patients on diuretic therapy, especially if high doses were used or if recently instituted; those on dietary salt restriction; renal dialysis patients). Volume and/or sodium depletion should be corrected prior to initiating therapy with AR antagonists, and the patient should be hemodynamically stable. Ideally, patients at risk for excessive hypotension should initiate AR antagonist therapy under close medical supervision, preferably with a lower dose, and followed closely for the first 2 weeks of treatment and whenever the dosage of AR antagonist or diuretic is increased.

Hypotension

Moderate:

prazosin

Prazosin has a moderate potential interaction with Hypotension.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

Liver Disease

Moderate:

prazosin

Prazosin has a moderate potential interaction with Liver Disease.

Little data exist concerning the pharmacokinetic disposition of prazosin in patients with liver disease. Prazosin is known to be metabolized by the liver and subsequently excreted in the bile, primarily as metabolites. Some of the metabolites are pharmacologically active and possess 10% to 25% of the hypotensive activity of prazosin. Therapy with prazosin should be administered cautiously in patients with significantly impaired hepatic or biliary function, since drug and/or metabolite accumulation may occur.

Renal Dysfunction

Moderate:

Avapro

The irbesartan in Avapro has a moderate potential interaction with Renal Dysfunction.

Changes in renal function including acute renal failure can be caused by drugs that inhibit the renin-angiotensin system and by diuretics. Patients whose renal function may depend in part on the activity of the renin-angiotensin system (e.g., patients with renal artery stenosis, chronic kidney disease, severe congestive heart failure, or volume depletion) may be at particular risk of developing acute renal failure with these agents. Monitor renal function periodically in these patients. Consider withholding or discontinuing therapy in patients who develop a clinically significant decrease in renal function with these agents.

Syncope

Moderate:

prazosin

Prazosin has a moderate potential interaction with Syncope.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

Vomiting

Moderate:

prazosin

Prazosin has a moderate potential interaction with Vomiting.

Peripheral alpha 1- adrenergic receptor blocking agents (aka alpha 1- blockers) cause vasodilation and can produce marked hypotension, especially orthostatic hypotension with syncope or other postural symptoms such as dizziness, lightheadedness, and palpitations. Orthostatic effects are most common during initiation of therapy and often occur within 90 minutes after the first dose. However, they can also occur following a dosage increase or resumption of therapy after an interruption of more than a few days. Agents with alpha 1a specificity, such as tamsulosin, act primarily on the prostate but are not devoid of hypotensive effects. Therapy with peripheral alpha-1 blockers should be administered cautiously in patients with or predisposed to hypotensive or syncopal episodes. Caution is also advised in patients who are dehydrated (e.g., due to severe or prolonged diarrhea or vomiting), since they may be more sensitive to the hypotensive effect of the drugs. Therapy should be initiated with the lowest dosage possible and titrated gradually based on patient response and tolerance in accordance with the individual product package labeling. During initiation or reinstitution of therapy and following an increase in dosage, patients should be advised not to rise abruptly from a sitting or recumbent position and to avoid situations where injury could result if syncope occur. Concomitant use of alcohol, extensive periods of standing, prolonged or intense exercise, and exposure to heat can also precipitate orthostatic hypotension and should be minimized. If dizziness, lightheadedness or palpitations occur, the patient should sit or lie down, and seek medical attention if symptoms are recurrent or bothersome.

More resources

Avapro

A total of 341 drugs are known to interact with Avapro.

prazosin

A total of 351 drugs are known to interact with prazosin.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.