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Drug Interactions between Rapaflo and tamsulosin

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

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Interactions between your drugs

Moderate

tamsulosin silodosin

Applies to: tamsulosin and Rapaflo (silodosin)

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

silodosin food

Applies to: Rapaflo (silodosin)

ADJUST DOSING INTERVAL: Food may reduce the oral bioavailability of silodosin. The effect of a moderate-fat, moderate-calorie meal on silodosin pharmacokinetics was variable and decreased silodosin maximum plasma concentration (Cmax) by approximately 18% to 43% and systemic exposure (AUC) by 4% to 49% across three different studies. The maximum effect of food (i.e., coadministration with a high-fat, high-calorie meal) on the pharmacokinetics of silodosin was not evaluated. Safety and efficacy clinical trials for silodosin were always conducted in the presence of food intake.

MANAGEMENT: Patients should be instructed to take silodosin with a meal to reduce the risk of adverse events.

References

  1. "Product Information. Rapaflo (silodosin)." Watson Pharmaceuticals (2008):

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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:

  • Rapaflo (silodosin)
  • 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.

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