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Drug Interactions between Cardura XL and tamsulosin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

doxazosin tamsulosin

Applies to: Cardura XL (doxazosin) and tamsulosin

GENERALLY AVOID: Additive pharmacodynamic effects may be expected when relatively selective alpha-1A adrenoreceptor antagonists are coadministered with other alpha-blockers. Clinical data have not been reported, but there may be an increased risk and/or severity of adverse effects related to blockade of alpha-1 adrenergic receptors in the peripheral vasculature such as postural hypotension, dizziness, headache, syncope, priapism, and nasal congestion. These effects have occurred with alpha-1A adrenoreceptor antagonists even when given alone for the treatment of benign prostatic hyperplasia, despite relative selectivity for the 1A subtype of alpha-1 adrenoreceptors located in prostatic and bladder tissues.

MANAGEMENT: The use of relatively selective alpha-1A adrenoreceptor antagonists in combination with other alpha-blockers should be avoided.

References

  1. "Product Information. Flomax (tamsulosin)." Boehringer-Ingelheim PROD (2001):
  2. "Product Information. Rapaflo (silodosin)." Watson Pharmaceuticals (2008):

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Drug and food interactions

Moderate

tamsulosin food

Applies to: tamsulosin

ADJUST DOSING INTERVAL: Food may delay the gastrointestinal absorption of tamsulosin. The time to maximum plasma concentration (Tmax) is reached by 4 to 5 hours under fasted conditions and by 6 to 7 hours when tamsulosin is administered with food. The delay in Tmax has the desirable effect of smoothing the tamsulosin plasma concentration profile, thereby reducing fluctuation of the plasma peak and trough concentrations with multiple dosing. Food may also affect the extent of absorption of tamsulosin. It has been reported that taking tamsulosin under fasted conditions results in a 30% increase in bioavailability (AUC) and 40% to 70% increase in peak plasma concentration (Cmax) compared to fed conditions. The effects of food on the pharmacokinetics of tamsulosin are consistent regardless of whether tamsulosin is taken with a light meal or a high-fat meal.

MANAGEMENT: To ensure uniformity of absorption, tamsulosin should be administered approximately one-half hour following the same meal each day.

References

  1. "Product Information. Flomax (tamsulosin)." Boehringer-Ingelheim PROD (2001):

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Moderate

doxazosin food

Applies to: Cardura XL (doxazosin)

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

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

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Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Alpha-adrenoreceptor antagonists

Therapeutic duplication

The recommended maximum number of medicines in the 'alpha-adrenoreceptor antagonists' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'alpha-adrenoreceptor antagonists' category:

  • Cardura XL (doxazosin)
  • tamsulosin

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

See also

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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.

Medical Disclaimer