Drug Interactions between conivaptan and tamsulosin
This report displays the potential drug interactions for the following 2 drugs:
- conivaptan
- tamsulosin
Interactions between your drugs
tamsulosin conivaptan
Applies to: tamsulosin and conivaptan
GENERALLY AVOID: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of tamsulosin, which is primarily metabolized by the hepatic microsomal isoenzymes CYP450 3A4 and 2D6. Severe hypotension and priapism may occur. In 24 healthy volunteers, administration of a single 0.4 mg dose of tamsulosin with the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily for 5 days) resulted in a 2.2-fold increase in tamsulosin peak plasma concentration (Cmax) and 2.8-fold increase in systemic exposure (AUC). The magnitude of interaction may be increased further in individuals who have genetic polymorphisms of CYP450 2D6 resulting in reduced or absent enzyme activity, or so-called CYP450 2D6 poor metabolizers (approximately 7% of Caucasians and less than 2% of Asians and individuals of African descent). When a single 0.4 mg dose of tamsulosin was given to 24 healthy volunteers with the potent CYP450 2D6 inhibitor paroxetine (20 mg once daily for 9 days), tamsulosin Cmax and AUC increased by a factor of 1.3 and 1.6, respectively. A similar increase in exposure is expected in CYP450 2D6 poor metabolizers as compared to extensive metabolizers, hence a potentially greater impact of CYP450 3A4 inhibition.
MANAGEMENT: Since CYP450 2D6 poor metabolizers cannot be readily identified, concomitant use of tamsulosin with potent CYP450 3A4 inhibitors should generally be avoided. Some authorities recommend avoiding concomitant use of tamsulosin during and for 2 weeks after treatment with itraconazole. If tamsulosin administration is discontinued for several days or more at either the 0.4 or 0.8 mg dose, therapy should be reinitiated with the 0.4 mg once-daily dose and titrated gradually as needed.
References
- (2002) "Product Information. Sporanox (itraconazole)." Janssen Pharmaceuticals
- (2001) "Product Information. Flomax (tamsulosin)." Boehringer-Ingelheim
- Cerner Multum, Inc. "Australian Product Information."
- Franco-Salinas G, de la Rosette JJ, Michel MC (2010) "Pharmacokinetics and pharmacodynamics of tamsulosin in its modified-release and oral controlled absorption system formulations." Clin Pharmacokinet, 49, p. 177-88
- Kamimura H, Oishi S, Matsushima H, et al. (1998) "Identification of cytochrome P450 isozymes involved in metabolism of the alpha1-adrenoceptor blocker tamsulosin in human liver microsomes." Xenobiotica, 28, p. 909-22
Drug and food interactions
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
- (2001) "Product Information. Flomax (tamsulosin)." Boehringer-Ingelheim
Therapeutic duplication warnings
No warnings were found for your selected drugs.
Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
See also
Drug Interaction Classification
Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
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. | |
No interaction information available. |
Further information
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